Me. Chief Justice Stone

delivered the opinion of the Court.

The Arizona Train Limit Law of May 16, 1912, Arizona Code Ann., 1939, § 69-119, makes it unlawful for any person or corporation to operate within the state a railroad train of more than fourteen passenger or seventy freight cars, and authorizes the state to recover a money penalty for each violation of the Act. The questions for decision are whether Congress has, by legislative enactment, restricted the power of the states to regulate the length of interstate trains as a safety measure and, if not, whether the statute contravenes the commerce clause of the Federal Constitution.

In 1940 the State of Arizona brought suit in the Arizona Superior Court against appellant, the Southern Pacific Company, to recover the statutory penalties for operating within the state two interstate trains, one a passenger train of more than fourteen cars, and one a freight train of more than seventy cars. Appellant answered, admitting the train operations, but defended on the ground that the statute offends against the commerce clause and the due process clause of the Fourteenth Amendment and conflicts with federal legislation. After an extended trial, *764without a jury, the court made detailed findings of fact on the basis of which it gave judgment for the railroad company. The Supreme Court of Arizona reversed and directed judgment for the state. 61 Ariz. 66, 145 P. 2d 530. The case comes here on appeal under § 237 (a) of the Judicial Code, appellant raising by its assignments of error the questions presented here for decision.

The Supreme Court left undisturbed the findings of the trial court and made no new findings. It held that the power of the state to regulate the length of interstate trains had not been restricted by Congressional action. It sustained the Act as a safety measure to reduce the number of accidents attributed to the operation of trains of more than the statutory maximum length, enacted by the state legislature in the exercise of its “police power.” This power the court held extended to the regulation of the operations of interstate commerce in the interests of local health, safety and well-being. It thought that a state statute, enacted in the exercise of the police power, and bearing some reasonable relation to the health, safety and well-being of the people of the state, of which the state legislature is the judge, was not to be judicially overturned, notwithstanding its admittedly adverse effect on the operation of interstate trains.

Purporting to act under § 1, paragraphs 10-17 of the Interstate Commerce Act, 24 Stat. 379 as amended (49 U. S. C. § 1 et seq.), the Interstate Commerce Commission, as of September 15, 1942, promulgated as an emergency measure Service Order No. 85, 7 Fed. Reg. 7258, suspending the operation of state train limit laws for the duration of the war, and denied an application to set aside the order. In the Matter of Service Order No. 85, 256 I. C. C. 523. Paragraph 15 of § 1 of the Interstate Commerce Act empowers the Commission, when it is “of opinion that shortage of equipment, congestion of traffic, or other emergency requiring immediate action exists in any *765section of the country,” to make or suspend rules and practices “with respect to car service,” which includes by paragraph 10 of § 1 “the use, control, supply, movement, distribution, exchange, interchange, and return” of locomotives and cars, and the “supply of trains.” Paragraph 16 of § 1 provides that when a carrier is unable properly to transport the traffic offered, the Commission may make reasonable directions “with respect to the handling, routing, and movement of the traffic of such carrier and its distribution over other lines of roads.” The authority of the Commission to make Order No. 85 is currently under attack in Johnston v. United States, Civil Action No. 1408, pending in the Western District of Oklahoma.

The Commission’s order was not in effect in 1940 when the present suit was brought for violations of the state law in that year, and the Commission’s order is inapplicable to the train operations here charged as violations. Hence the question here is not of the effect of the Commission’s order, which we assume for purposes of decision to be .valid, but whether the grant of power to the Commission operated to supersede the state act before the Commission’s order. We are of opinion that, in the absence of administrative implementation by the Commission, § 1 does not of itself curtail state power to regulate train lengths. The provisions under which the Commission purported to act, phrased in broad and general language, do not in terms deal with that subject. We do not gain either from their words or from the legislative history any hint that Congress in enacting them intended, apart from Commission action, to supersede state laws regulating train lengths. We can hardly suppose that Congress, merely by conferring authority on the Commission to regulate car service in an “emergency,” intended to restrict the exercise, otherwise lawful, of state power to regulate train lengths before the Commission finds an “emergency” to exist.

*766Congress, in enacting legislation within its constitutional authority over interstate commerce, will not be deemed to have intended to strike down a state statute designed to protect the health and safety of the public unless its purpose to do so is clearly manifested, Reid v. Colorado, 187 U. S. 137, 148; Missouri Pacific R. Co. v. Larabee Mills, 211 U. S. 612, 621, et seq.; Missouri, K. & T. R. Co. v. Harris, 234 U. S. 412, 418-419; Welch Co. v. New Hampshire, 306 U. S. 79,85; Allen-Bradley Local v. Board, 315 U. S. 740, 749, or unless the state law, in terms or in its practical administration, conflicts with the Act of Congress, or plainly and palpably infringes its policy. Sinnot v. Davenport, 22 How. 227, 243; Missouri, K. & T. R. Co. v. Haber, 169 U. S. 613, 623; Savage v. Jones, 225 U. S. 501, 533; Carey v. South Dakota, 250 U. S. 118, 122; Atchison, T. & S. F. R. Co. v. Railroad Comm’n, 283 U. S. 380, 391; Townsend v. Yeomans, 301 U. S. 441, 454.

The contention, faintly urged, that the provisions of the Safety Appliance Act, 45 U. S. C. §§ 1 and 9, providing for brakes on trains, and of § 25 of Part I of the Interstate Commerce Act, 49 U. S. C. § 26 (b), permitting the Commission to order the installation of train stop and control devices, operate of their own force to exclude state regulation of train lengths, has even less support. Congress, although asked to do so,1 has declined to pass legislation specifically limiting trains to seventy cars. We are therefore brought to appellant’s principal contention, that the state statute contravenes the commerce clause of the Federal Constitution.

Although the commerce clause conferred on the national government power to regulate commerce, its possession of the power does not exclude all state power of regulation. Ever since Willson v. Black-Bird Creek Marsh *767 Co., 2 Pet. 245, and Cooley v. Board of Wardens, 12 How. 299, it has been recognized that, in the absence of conflicting legislation by Congress, there is a residuum of power in the state to make laws governing matters of local concern which nevertheless in some measure affect interstate commerce or even, to some extent, regulate it. Minnesota Rate Cases, 230 U. S. 352, 399-400; South Carolina Highway Dept. v. Barnwell Bros., 303 U. S. 177, 187, et seq.; California v. Thompson, 313 U. S. 109, 113-14 and cases cited; Parker v. Brown, 317 U. S. 341, 359-60. Thus the states may regulate matters which, because of their number and diversity, may never be adequately dealt with by Congress. Cooley v. Board of Wardens, supra, 319; South Carolina Highway Dept. v. Barnwell Bros., supra, 185; California v. Thompson, supra, 113; Duckworth v. Arkansas, 314 U. S. 390, 394; Parker v. Brown, supra, 362, 363. When the regulation of matters of local concern is local in character and effect, and its impact on the national commerce does not seriously interfere with its operation, and the consequent incentive to deal with them nationally is slight, such regulation has been generally held to be within state authority. South Carolina Highway Dept. v. Barnwell Bros., supra, 188 and cases cited; Lone Star Gas Co. v. Texas, 304 U. S. 224, 238; Milk Board v. Eisenberg Co., 306 U. S. 346, 351; Maurer v. Hamilton, 309 U. S. 598, 603; California v. Thompson, supra, 113-14 and cases cited.

But ever since Gibbons v. Ogden, 9 Wheat. 1, the states have not been deemed to have authority to impede substantially the free flow of commerce from state to state, or to regulate those phases of the national commerce which, because of the need of national uniformity, demand that their regulation, if any, be prescribed by a single authority.2 Cooley v. Board of Wardens, supra, 319; Leisy *768v. Hardin, 135 U. S. 100, 108, 109; Minnesota Rate Cases, supra, 399-400; Edwards v. California, 314 U. S. 160, 176. Whether or not this long-recognized distribution of power between the national and the state governments is predicated upon the implications of the commerce clause itself, Brown v. Maryland, 12 Wheat. 419, 447; Minnesota Rate Cases, supra, 399, 400; Pennsylvania v. West Virginia, 262 U. S. 553, 596; Baldwin v. Seelig, 294 U. S. 511, 522; South Carolina Highway Dept. v. Barnwell Bros., supra, 185, or upon the presumed intention of Congress, where Congress has not spoken, Welton v. Missouri, 91 U. S. 275, 282; Hall v. DeCuir, 95 U. S. 485, 490; Brown v. Houston, 114 U. S. 622, 631; Bowman v. Chicago & N. W. R. Co., 125 U. S. 465, 481-2; Leisy v. Hardin, supra, 109; In re Rahrer, 140 U. S. 545, 559-60; Brennan v. Titusville, 153 U. S. 289, 302; Covington & C. Bridge Co. v. Kentucky, 154 U. S. 204, 212; Graves v. New York ex rel. O’Keefe, 306 U. S. 466, 479, n., Dowling, Interstate Commerce and State Power, 27 Va. Law Rev. 1, the result is the same.

In the application of these principles some enactments may be found to be plainly within and others plainly without state power. But between these extremes lies the infinite variety of cases, in which regulation of local matters may also operate as a regulation of commerce, in which reconciliation of the conflicting claims of state and' *769national power is to be attained only by some appraisal and accommodation of the competing demands of the state and national interests involved. Parker v. Brown, supra, 362; Terminal Railroad Assn. v. Brotherhood, 318 U. S. 1, 8; see DiSanto v. Pennsylvania, 273 U. S. 34, 44 (and compare California v. Thompson, supra); Illinois Gas Co. v. Public Service Co., 314 U. S. 498, 504-5.

For a hundred years it has been accepted constitutional doctrine that the commerce clause, without the aid of Congressional legislation, thus affords some protection from state legislation inimical to the national commerce, and that in such cases, where Congress has not acted, this Court, and not the state legislature, is under the commerce clause the final arbiter of the competing demands of state and national interests. Cooley v. Board of Wardens, supra; Kansas City Southern R. Co. v. Kaw Valley District, 233 U. S. 75, 79; South Covington R. Co. v. Covington, 235 U. S. 537, 546; Missouri, K. & T. R. Co. v. Texas, 245 U. S. 484, 488; St. Louis & S. F. R. Co. v. Public Service Comm’n, 254 U. S. 535, 537; Foster-Fountain Packing Co. v. Haydel, 278 U. S. 1, 10; Gwin, White & Prince v. Henneford, 305 U. S. 434, 441; McCarroll v, Dixie Lines, 309 U. S. 176.

Congress has undoubted power to redefine the distribution of power over interstate commerce. It may either permit the states to regulate the commerce in a manner which would otherwise not be permissible, In re Rahrer, supra, 561-62; Adams Express Co. v. Kentucky, 238 U. S. 190, 198; Rosenberger v. Pacific Express Co., 241 U. S. 48, 50, 51; Clark Distilling Co. v. Western Maryland R. Co., 242 U. S. 311, 325-6; Whitfield v. Ohio, 297 U. S. 431, 438-40; Kentucky Whip & Collar Co. v. Illinois Central R. Co., 299 U. 334, 350-51; Hooven & Allison Co. v. Evatt, 324 U. S. 652, 679, or exclude state regulation even of matters of peculiarly local concern which nevertheless affect interstate commerce. . Addyston Pipe & Steel Co. v. *770 United States, 175 U. S. 211, 230; Louisville & Nashville R. Co. v. Mottley, 219 U. S. 467; Houston, E. & W. T. R. Co. v. United States, 234 U. S. 342; American Express Co. v. Caldwell, 244 U. S. 617, 626; Illinois Central R. Co. v. Public Utilities Comm’n, 245 U. S. 493, 506; New York v. United States, 257 U. S. 591, 601; Louisiana Public Service Comm’n v. Texas & N. O. R. Co., 284 U. S. 125, 130; Pennsylvania R. Co. v. Illinois Brick Co., 297 U. S. 447, 459.

But in general Congress has left it to the courts to formulate the rules thus interpreting the commerce clause in its application, doubtless because it has appreciated the destructive consequences to the commerce of the nation if their protection were withdrawn, Gwin, White & Prince v. Henneford, supra, 441, and has been aware that in their application state laws will not be invalidated without the support of relevant factual material which will “afford a sure basis” for an informed judgment. Terminal Railroad Assn. v. Brotherhood, supra, 8; Southern R. Co. v. King, 217 U. S. 524. Meanwhile, Congress has accommodated its legislation, as have the states, to these rules as an established feature of our constitutional system. There has thus been left to the states wide scope for the regulation of matters of local state concern, even though it in some measure affects the commerce, provided it does not materially restrict the free flow of commerce across state lines, or interfere with it in matters with respect to which uniformity of regulation is of predominant national concern.

Hence the matters for ultimate determination here are the nature and extent of the burden which the state regulation of interstate trains, adopted as a safety measure, imposes on interstate commerce, and whether the relative weights of the state and national interests involved are such as to make inapplicable the rule, generally observed, that the free flow of interstate commerce and its freedom *771from local restraints in matters requiring uniformity of regulation are interests safeguarded by the commerce clause from state interference.

While this Court is not bound by the findings of the state court, and may determine for itself the facts of a case upon which an asserted federal right depends, Hooven & Allison Co. v. Evatt, supra, p. 659, and cases cited, the facts found by the state trial court showing the nature of the interstate commerce involved, and the effect upon it of the train limit law, are not seriously questioned. Its findings with respect to the need for and effect of the statute as a safety measure, although challenged in some particulars which we do not regard as material to our decision, are likewise supported by evidence. Taken together the findings supply an adequate basis for decision of the constitutional issue.

The findings show that the operation of long trains, that is trains of more than fourteen passenger and more than seventy freight cars, is standard practice over the main lines of the railroads of the United States, and that, if the length of trains is to be regulated at all, national uniformity in the regulation adopted, such as only Congress can prescribe, is practically indispensable to the operation of an efficient and economical national railway system. On many railroads passenger trains of more than' fourteen cars and freight trains of more than seventy cars are operated, and on some systems freight trains are run ranging from one hundred and twenty-five to one hundred and sixty cars in length. Outside of Arizona, where the length of trains is not. restricted, appellant runs a substantial proportion of long trains. In 1939 on its comparable route for through traffic through Utah and Nevada from 66 to 85% of its freight trains were over seventy cars in length and over 43% of its passenger trains included more than fourteen passenger cars.

In Arizona, approximately 93% of the freight traffic and 95% of the passenger traffic is interstate. Because *772of the Train Limit Law appellant is required to haul over 30% more trains in Arizona than would otherwise have been necessary. The record shows a definite relationship between operating costs and the length of trains, the increase in length resulting in a reduction of operating costs per car. The additional cost of operation of trains complying with the Train Limit Law in Arizona amounts for the two railroads traversing that state to about $1,000,000 a year. The reduction in train lengths also impedes efficient operation. More locomotives and more manpower are required; the necessary conversion and reconversion of train lengths at terminals and the delay caused by breaking up and remaking long trains upon entering and leaving the state in order to comply with the law, delays the traffic and diminishes its volume moved in a given time, especially when traffic is heavy.

To relieve the railroads of these burdens, during the war emergency only, the Interstate Commerce Commission, acting under § 1 of the Interstate Commerce Act, suspended the operation of the state law for the duration of the war by its order of September 15, 1942, to which we have referred. In support of the order the Commission declared: “It was designed to save manpower, motive power, engine-miles and train-miles; to avoid delay in the movement of trains; to increase the efficient use of locomotives and cars and to augment the available supply thereof; and to relieve congestion at terminals caused by setting out and picking up cars on each side of the train-limit law States.” In the Matter of Service Order No. 85, 256 I. C. C. 523, 524. Appellant, because of its past compliance with the Arizona Train Limit Law, has been unable to avail itself fully of the benefits of the suspension order because some of its equipment and the length of its sidings in Arizona are not suitable for the operation of long trains. Engines capable of hauling long trains were not in service. It can engage in long *773train operations to the best advantage only by rebuilding its road to some extent and by changing or adding to its motive power equipment, which it desires to do in order to secure more efficient and economical operation of its trains.

The unchallenged findings leave no doubt that the Arizona Train Limit Law imposes a serious burden on the interstate commerce conducted by appellant. It materially impedes the movement of appellant’s interstate trains through that state and interposes a substantial obstruction to the national policy proclaimed by Congress, to promote adequate, economical and efficient railway transportation service. Interstate Commerce Act, preceding § 1, 54 Stat. 899. Enforcement of the law in Arizona, while train lengths remain unregulated or are regulated by varying standards in other states, must inevitably result in an impairment of uniformity of efficient railroad operation because the railroads are subjected to regulation which is not uniform in its application. Compliance with a state statute limiting train lengths requires interstate trains of a length lawful in other states to be broken up and reconstituted as they enter each state according as it may impose varying limitations upon train lengths. The alternative is for the carrier to conform to the lowest train limit restriction of any of the states through which its trains pass, whose laws thus control the carriers’ operations both within and without the regulating state.

Although the seventy car maximum for freight trains is the limitation which has been most commonly proposed, various bills introduced in the state legislatures provided for maximum freight train lengths of from fifty to one hundred and twenty-five cars, and maximum passenger train lengths of from ten to eighteen cars.3 With such *774laws in force in states which are interspersed with those having no limit on train lengths, the confusion and difficulty with which interstate operations would be burdened under the varied system of state regulation and the unsatisfied need for uniformity in such regulation, if any, are evident.4

At present the seventy freight car laws are enforced only in Arizona and Oklahoma, with a fourteen car passenger car limit in Arizona. The record here shows that the enforcement of the Arizona statute results in freight trains being broken up and reformed at the California border and in New Mexico, some distance from the Arizona line. Frequently it is not feasible to operate a newly assembled train from the New Mexico yard nearest to Arizona, with the result that the Arizona limitation governs the flow of traffic as far east as El Paso, Texas. For similar reasons the Arizona law often controls the *775length of passenger trains all the way from Los Angeles to El Paso.5

If one state may regulate train lengths, so may all the others, and they need not prescribe the same maximum limitation. The practical effect of such regulation is to control train operations beyond the boundaries of the state exacting it because of the necessity of breaking up and reassembling long trains at the nearest terminal points before entering and after leaving the regulating state. The serious impediment to the free flow of commerce by the local regulation of train lengths and the practical necessity that such regulation, if any, must be prescribed by a single body having a nation-wide authority are apparent.

The trial court found that the Arizona law had no reasonable relation to safety, and made train operation more dangerous. Examination of the evidence and the detailed findings makes it clear that this conclusion was rested on facts found which indicate that such increased danger of accident and personal injury as may result from the greater length of trains is more than offset by the increase in the number of accidents resulting from the larger number of trains when train lengths are reduced. In considering the effect of the statute as a safety measure, therefore, the factor of controlling significance for present purposes is not whether there is basis for the conclusion of the Arizona Supreme Court that the increase in length of trains beyond the statutory maximum has an adverse effect upon safety of operation. The decisive question is whether in the circumstances the total effect of the *776law as a safety measure in reducing accidents and casualties is so slight or problematical as not to outweigh the national interest in keeping interstate commerce free from interferences which seriously impede it and subject it to local regulation which does not have a uniform effect on the interstate train journey which it interrupts.

The principal source of danger of accident from increased length of trains is the resulting increase of “slack action” of the train. Slack action is the amount of free movement of one car before it transmits its motion to an adjoining coupled car. This free movement results from the fact that in railroad practice cars are loosely coupled, and the coupling is often combined with a shock-absorbing device, a “draft gear,” which, under stress, substantially increases the free movement as the train is started or stopped. Loose coupling is necessary to enable the train to proceed freely around curves and is an aid in starting heavy trains, since the application of the locomotive power to the train operates on each car in the train successively, and the power is thus utilized to start only one car at a time.

The slack action between cars due to loose couplings varies from seven-eighths of an inch to one and one-eighth inches and, with the added free movement due to the use of draft gears, may be as high as six or seven inches between cars. The length of the train increases the slack since the slack action of a train is the total of the free movement between its several cars. The amount of slack action has some effect on the severity of the shock of train movements, and on freight trains sometimes results in injuries to operatives, which most frequently occur to occupants of the caboose. The amount and severity of slack action, however, are not wholly dependent upon the length of train, as they may be affected by the mode and conditions of operation as to grades, speed, and load. And accidents due to slack action also occur in the opera*777tion of short trains. On comparison of the number of slack action accidents in Arizona with those in Nevada, where the length of trains is now unregulated, the trial court found that with substantially the same amount of traffic in each state the number of accidents was relatively the same in long as in short train operations. While accidents from slack action do occur in the operation of passenger trains, it does not appear that they are more frequent or the resulting shocks more severe on long than on short passenger trains. Nor does it appear that slack action accidents occurring on passenger trains, whatever their length, are of sufficient severity to cause serious injury or damage.

As the trial court found, reduction of the length of trains also tends to increase the number of accidents because of the increase in the number of trains. The application of the Arizona law compelled appellant to operate 30.08%, or 4,304, more freight trains in 1938 than would otherwise have been necessary. And the record amply supports the trial court’s conclusion that the frequency of accidents is closely related to the number of trains run. The number of accidents due to grade crossing collisions between trains and motor vehicles and pedestrians, and to collisions between trains, which are usually far more serious than those due to slack action, and accidents due to locomotive failures, in general vary with the number of trains.6 Increase in the number of trains results in more starts and stops, more “meets” and “passes,” and more switching movements, all tending to increase the number *778of accidents not only to train operatives and other railroad employees, but to passengers and members of the public exposed to danger by train operations.

Railroad statistics introduced into the record tend to show that this is the result of the application of the Arizona Train Limit Law to appellant, both with respect to all railroad casualties within the state and those affecting only trainmen whom the train limit law is supposed to protect. The accident rate in Arizona is much higher than on comparable lines elsewhere, where there is no regulation of length of trains. The record lends support to the trial court’s conclusion that the train length limitation increased rather than diminished the number of accidents. This is shown by comparison of appellant’s operations in Arizona with those in Nevada,7 and by comparison of operations of appellant and of the Santa Fe Railroad in Arizona with those of the same roads in New Mexico,8 and by like comparison between appellant’s operations in Arizona and operations throughout the country.9

*779Upon an examination of the whole case the trial court found that “if short-train operation may or should result in any decrease in the number or severity of the ‘slack’ or ‘slack-surge’ type of accidents or casualties, such decrease is substantially more than offset by the increased number of accidents and casualties from other causes that follow the arbitrary limitation of freight trains to 70 cars . . . and passenger trains to 14 cars.”

We think, as the trial court found, that the Arizona Train Limit Law, viewed as a safety measure, affords at most slight and dubious advantage, if any, over unregulated train lengths, because it results in an increase in the number of trains and train operations and the consequent increase in train accidents of a character generally more severe than those due to slack action. Its undoubted effect on the commerce is the regulation, without securing uniformity, of the length of trains operated in interstate commerce, which lack is itself a primary cause of preventing the free flow of commerce by delaying it and by substantially increasing its cost and impairing its efficiency. In these respects the case differs from those where a state, by regulatory measures affecting the commerce, has removed or reduced safety hazards without substantial interference with the interstate movement of trains. Such are measures abolishing the car stove, New York, N. H. & H. R. Co. v. New York, 165 U. S. 628; requiring locomotives to be supplied with electric headlights, Atlantic Coast Line R. Co. v. Georgia, 234 U. S. 280; providing for full train crews, Chicago, R. I. & P. R. Co. v. Arkansas, 219 U. S. 453; St. Louis & I. M. R. Co. v. Arkansas, 240 U. S. 518; Missouri Pacific R. Co. v. Norwood, 283 U. S. 249; and for the equipment of freight trains with cabooses, Terminal Railroad Assn. v. Brotherhood, supra.

The principle that, without controlling Congressional action/ a state may not regulate interstate commerce so *780as substantially to affect its flow or’ deprive it of needed uniformity in its regulation is not to be avoided by “simply invoking the convenient apologetics of the police power,” Kansas City Southern R. Co. v. Kaw Valley District, supra, 79; Buck v. Kuykendall, 267 U. S. 307, 315. In the Kaw Valley case the Court held that the state was without constitutional power to order a railroad to remove a railroad bridge over which its interstate trains passed, as a means of preventing floods in the district and of improving its drainage, because it was “not pretended that local welfare needs the removal of the defendants’ bridges at the expense of the dominant requirements of commerce with other States, but merely that it would be helped by raising them.” And in Seaboard Air Line R. Co. v. Blackwell, 244 U. S. 310, it was held that the interference with interstate rail transportation resulting from a state statute requiring as a safety measure that trains come almost to a stop at grade crossings, outweigh the local interest in safety, when it appeared that compliance increased the scheduled running time more than six hours in a distance of one hundred and twenty-three miles. Cf. Southern R. Co. v. King, supra, where the crossings were less numerous and the burden to interstate commerce was not shown to be heavy; and see Erb v. Morasch, 177 U. S. 584.

Similarly the commerce clause has been held to invalidate local “police power” enactments fixing the number of cars in an interstate train and the number of passengers to be carried in each car, South Covington R. Co. v. Covington, supra, 547; regulating the segregation of colored passengers in interstate trains, Hall v. DeCuir, supra, 488-9; requiring burdensome intrastate stops of interstate trains, Illinois Central R. Co. v. Illinois, 163 U. S. 142; Cleveland, C., C. & St. L. R. Co. v. Illinois, 177 U. S. 514; Mississippi Railroad Comm’n v. Illinois Central R. Co., 203 U. S. 335; Herndon v. Chicago, R. I. & P. R. Co., *781218 U. S. 135; St. Louis-S. F. R. Co. v. Public Service Comm’n, 261 U. S. 369; requiring an interstate railroad to detour its through passenger trains for.the benefit of a small city, St. Louis & S. F. R. Co. v. Public Service Comm’n, supra; interfering with interstate commerce by requiring interstate trains to leave on time, Missouri, K. & T. R. Co. v. Texas, 245 U. S. 484; regulating car distribution to interstate shippers, St. Louis S. W. R. Co. v. Arkansas, 217 U. S. 136; or establishing venue provisions requiring railroads to defend accident suits at points distant from the place of injury and the residence and activities of the parties, Davis v. Farmers Co-operative Co., 262 U. S. 312; Michigan Central R. Co. v. Mix, 278 U. S. 492; cf. Denver & R. G. W. R. Co. v. Terte, 284 U. S. 284; see also Buck v. Kuykendall, supra; Foster-Fountain Packing Co. v. Haydel, supra; Baldwin v. Seelig, supra, 524; South Carolina Highway Dept. v. Barnwell Bros., supra, 184-5 n., and cases cited.

More recently in Kelly v. Washington, 302 U. S. 1, 15, we have pointed out that when a state goes beyond safety measures which are permissible because only local in their effect upon interstate commerce, and “attempts to impose particular standards as to structure, design, equipment and operation [of vessels plying interstate] which in the judgment of its authorities may be desirable but pass beyond what is plainly essential to safety and seaworthiness, the State will encounter the principle that such requirements, if imposed at all, must be through the action of Congress which can establish a uniform rule. Whether the State in a particular matter goes too far must be left to be determined when the precise question arises.”

Here we conclude that the state does go too far. Its regulation of train lengths, admittedly obstructive to interstate train operation, and having a seriously adverse effect on transportation efficiency and economy, passes beyond what is plainly essential for safety since it does *782not appear that it will lessen rather than increase the danger of accident. Its attempted regulation of the operation of interstate trains cannot establish nation-wide control such as is essential to the maintenance of an efficient transportation system, which Congress alone can prescribe. The state interest cannot be preserved at the expense of the national interest by an enactment which regulates interstate train lengths without securing such control, which is a matter of national concern. To this the interest of the state here asserted is subordinate.

Appellees especially rely on the full train crew eases, Chicago, R. I. & P. R. Co. v. Arkansas, supra; St. Louis & I. M. R. Co. v. Arkansas, supra; Missouri Pacific R. Co. v. Norwood, supra, and also on South Carolina Highway Dept. v. Barnwell Bros., supra, as supporting the state’s authority to regulate the length of interstate trains. While the full train crew laws undoubtedly placed an added financial burden on the railroads in order to serve a local interest, they did not obstruct interstate transportation or seriously impede it. They had no effects outside the state beyond those of picking up and setting down the extra employees at the state boundaries; they involved no wasted use of facilities or serious impairment of transportation efficiency, which are among the factors of controlling weight here. In sustaining those laws the Court considered the restriction a minimal burden on the commerce comparable to the law requiring the licensing of engineers as a safeguard against those of reckless and intemperate habits, sustained in Smith v. Alabama, 124 U. S. 465, or those afflicted with color blindness, upheld in Nashville, C. & St. L. R. Co. v. Alabama, 128 U. S. 96, and other similar regulations. New York, N. H. & H. R. Co. v. New York, supra; Atlantic Coast Line R. Co. v. Georgia, supra; cf. County of Mobile v. Kimball, 102 U. S. 691.

*783 South Carolina Highway Dept. v. Barnwell Bros., supra, was concerned with the power of the state to regulate the weight and width of motor cars passing interstate over its highways, a legislative field over which the state has a far more extensive control than over interstate railroads. In that case, and in Maurer v. Hamilton, supra, we were at pains to point out that there are few subjects of state regulation affecting interstate commerce which are so peculiarly of local concern as is the use of the state’s highways. Unlike the railroads local highways are built, owned and maintained by the state or its municipal subdivisions. The state is responsible for their safe and economical administration. Regulations affecting the safety of their use must be applied alike to intrastate and interstate traffic. The fact that they affect alike shippers in interstate and intrastate commerce in great numbers, within as well as without the state, is a safeguard against regulatory abuses. Their regulation is akin to quarantine measures, game laws, and like local regulations of rivers, harbors, piers, and docks, with respect to which the state has exceptional scope for the exercise of its regulatory power, and which, Congress not acting, have been sustained even though they materially interfere with interstate commerce (303 U. S. at 187-188 and cases cited).

The contrast between the present regulation and the full train crew laws in point of their effects on the commerce, and the like contrast with the highway safety regulations, in point of the nature of the subject of regulation and the state’s interest in it, illustrate and emphasize the considerations which enter into a determination of the relative weights of state and national interests where state regulation affecting interstate commerce is attempted. Here examination of all the relevant factors makes it plain that the state interest is outweighed by the interest of the nation in an adequate, economical *784and efficient railway transportation service, which must prevail.

Reversed.

Me. Justice Rutledge concurs in the result.

Me. Justice Black,

dissenting.

In Hennington v. Georgia, 163 U. S. 299, 304, a case which involved the power of a state to regulate interstate traffic, this Court said, “The whole theory of our government, federal and state, is hostile to the idea that questions of legislative authority may depend . . . upon opinions of judges as to the wisdom or want of wisdom in the enactment of laws under powers clearly conferred upon the legislature.” What the Court decides today is that it is unwise governmental policy to regulate the length of trains. I am therefore constrained to note my dissent.

For more than a quarter of a century, railroads and their employees have engaged in controversies over the relative virtues and dangers of long trains. Railroads have argued that they could carry goods and passengers cheaper in long trains than in short trains. They have also argued that while the danger of personal injury to their employees might in some respects be greater on account of the operation of long trains, this danger was more than offset by an increased number of accidents from other causes brought about by the operation of a much larger number of short trains. These arguments have been, and are now, vigorously denied. While there are others, the chief causes assigned for the belief that long, trains unnecessarily jeopardize the lives and limbs of railroad employees relate to “slack action.” Cars coupled together retain a certain free play of movement, ranging between 1 y2 inches and 1 foot, and this is called “slack action.” Train brakes do not ordinarily apply or release simultaneously on all cars. This frequently results in a severe *785shock or jar to cars, particularly those in the rear of a train. It has always been the position of the employees that the dangers from “slack action” correspond to and are proportionate with the length of the train. The argument that “slack movements” are more dangerous in long trains than in short trains seems never to have been denied. The railroads have answered it by what is in effect a plea of confession and avoidance. They say that the added cost of running short trains places an unconstitutional burden on interstate commerce. Their second answer is that the operation of short trains requires the use of more separate train units; that a certain number of accidents resulting in injury are inherent in the operation of each unit, injuries which may be inflicted either on employees or on the public; consequently, they have asserted that it is not in the public interest to prohibit the operation of long trains.

In 1912, the year Arizona became a state, its legislature adopted and referred to the people several safety measures concerning the operation of railroads. One of these required railroads to install electric headlights, a power which the state had under this Court's opinion in Atlantic Coast Line R. Co. v. Georgia, 234 U. S. 280. Another Arizona safety statute submitted at the same time required certain tests and service before a person could act as an engineer or train conductor, and thereby exercised a state power similar to that which this Court upheld in Nashville, C. & St. L. R. Co. v. Alabama, 128 U. S. 96. The third safety statute which the Arizona legislature submitted to the electorate, and which was adopted by it, is the train limitation statute now under consideration. By its enactment the legislature and the people adopted the viewpoint that long trains were more dangerous than short trains, and limited the operation of train units to 14 cars for passenger and 70 cars for freight. This same question was considered in other states, and some of them, *786over the vigorous protests of railroads, adopted laws similar to the Arizona statute.1

This controversy between the railroads and their employees, which was nation-wide, was carried to Congress. Extensive hearings took place. The employees' position was urged by members of the various Brotherhoods. The railroads’ viewpoint was presented through representatives of their National Association. In 1937, the Senate Interstate Commerce Committee after its own exhaustive hearings unanimously recommended that trains be limited to 70 cars as a safety measure.2 The Committee in its Report reviewed the evidence and specifically referred to the large and increasing number of injuries and deaths suffered by railroad employees; it concluded that the admitted danger from slack movement was greatly intensified by the operation of long trains; that short trains reduce this danger; that the added cost of short trains to the railroad was no justification for jeopardizing the safety of railroad employees; and that the legislation would provide a greater degree of safety for persons and property, increase protection for railway employees and the public, and improve transportation services for shippers and consumers. The Senate passed the bill3 but the House Committee failed to report it out.

During the hearings on that measure, frequent references were made to the Arizona statute! It is significant, however, that American railroads never once asked Congress to exercise its unquestioned power to enact uniform legislation on that subject, and thereby invalidate the *787Arizona law. That which for some unexplained reason they did not ask Congress to do when it had the very subject of train length limitations under consideration, they shortly thereafter asked an Arizona state court to do.

In the state court a rather extraordinary “trial” took place. Charged with violating the law, the railroad admitted the charge. It alleged that the law was unconstitutional, however, and sought a trial of facts on that issue. The essence of its charge of unconstitutionality rested on one of these two grounds: (1) the legislature and people of Arizona erred in 1912 in determining that the running of long trains was dangerous; or (2) railroad conditions had so improved since 1912 that previous dangers did not exist to the same extent, and that the statute should be stricken down either because it cast an undue burden on interstate commerce by reason of the added cost, or because the changed conditions had rendered the Act “arbitrary and unreasonable.” Thus, the issue which the court “tried” was not whether the railroad was guilty of violating the law, but whether the law was unconstitutional either because the legislature had been guilty of misjudging the facts concerning the degree of the danger of long trains, or because the 1912 conditions of danger no longer existed.

Before the state trial court finally determined that the dangers found by the legislature in 1912 no longer existed, it heard evidence over a period of 5% months which appears in about 3,000 pages of the printed record before us. It then adopted findings of fact submitted to it by the railroad, which cover 148 printed pages, and conclusions of law which cover 5 pages. We can best understand the nature of this “trial” by analogizing the same procedure to a defendant charged with violating a state or national safety appliance act, where the defendant comes into court and admits violation of the act. In such cases, the ordinary procedure would be for the court to pass upon *788the constitutionality of the act, and either discharge or convict the defendants. The procedure here, however, would justify quite a different trial method. Under it, a defendant is permitted to offer voluminous evidence to show that a legislative body has erroneously resolved disputed facts in finding a danger great enough to justify the passage of the law. This new pattern of trial procedure makes it necessary for a judge to hear all the evidence offered as to why a legislature passed a law and to make findings of fact as to the validity of those reasons. If under today’s ruling a court does make findings, as to a danger contrary to the findings of the legislature, and the evidence heard “lends support” to those findings, a court can then invalidate the law. In this respect, the Arizona County Court acted, and this Court today is acting, as a “super-legislature.”4

*789Even if this method of invalidating legislative acts is a correct one, I still think that the “findings” of the state court do not authorize today’s decision. That court did not find that there is no unusual danger from slack movements in long trains. It did decide on disputed evidence that the long train “slack movement” dangers were more than offset by prospective dangers as a result of running a larger number of short trains, since many people might be hurt at grade crossings. There was undoubtedly some evidence before the state court from which it could have reached such a conclusion. There was undoubtedly as much evidence before it which would have justified a different conclusion.

Under those circumstances, the determination of whether it is in the interest of society for the length of trains to be governmentally regulated is a matter of public policy. Someone must fix that policy — either the Congress, or the state, or the courts. A century and a half of constitutional history and government admonishes this Court to leave that choice to the elected legislative representatives of the people themselves, where it properly belongs both on democratic principles and the requirements of efficient government.

I think that legislatures, to the exclusion of courts, have the constitutional power to enact laws limiting train lengths, for the purpose of reducing injuries brought about by “slack movements.” Their power is not less because a requirement of short trains might increase grade crossing accidents. This latter fact raises an entirely different *790element of danger which is itself subject to legislative regulation. For legislatures may, if necessary, require railroads to take appropriate steps to reduce the likelihood of injuries at grade crossings. Denver & R. G. R. Co. v. Denver, 250 U. S. 241. And the fact that grade-crossing improvements may be expensive is no sufficient reason to say that an unconstitutional “burden” is put upon a railroad even though it be an interstate road. Erie R. Co. v. Public Utility Commissioners, 254 U. S. 394, 408-411.

The Supreme Court of Arizona did not discuss the County Court’s so-called findings of fact. It properly designated the Arizona statute as a safety measure, and finding that it bore a reasonable relation to its purpose declined to review the judgment of the legislature as to the necessity for the passage of the act. In so doing it was well fortified by a long line of decisions of this Court. Today’s decision marks an abrupt departure from that line of cases.

There have been many sharp divisions of this Court concerning its authority, in the absence of congressional enactment, to invalidate state laws as violating the Commerce Clause. See e. g., Adams Manufacturing Co. v. Storen, 304 U. S. 307; Gwin, White & Prince v. Henneford, 305 U. S. 434; McCarroll v. Dixie Greyhound Lines, 309 U. S. 176. That discussion need not be renewed here, because even the broadest exponents of judicial power in this field have not heretofore expressed doubt as to a state’s power, absent a paramount congressional declaration, to regulate interstate trains in the interest of safety. For as early as 1913, this Court, speaking through Mr. Justice Hughes, later Chief Justice, referred to “the settled principle that, in the absence of legislation by Congress, the states are not denied the exercise of their power to secure safety in the physical operation of railroad trains within their territory, even though such trains are used in interstate commerce. That has been the law *791since the beginning of railroad transportation.” Atlantic Coast Line R. Co. v. Georgia, 234 U. S. 280, 291. Until today, the oft-repeated principles of that case have never been repudiated in whole or in part.

But, it is said today, the principle there announced does not apply because if one state applies a regulation of its own to interstate trains, “uniformity” in regulation or rather non-regulation, is destroyed. Justice Hughes speaking for the Court in the Atlantic Coast Line case made short shrift of that same argument. He there referred to the contention that “if state requirements conflict, it will be necessary to carry additional apparatus and to make various adjustments at state lines which would delay and inconvenience interstate traffic.” In answer to this argument he reiterated a former declaration of this Court in New York, N. H. & H. R. Co. v. New York, 165 U. S. 628, on this subject, and added that “If there is a conflict in such local regulations, by which interstate commerce may be inconvenienced — if there appears to be need of standardization of safety appliances and of providing rules of operation which will govern the entire interstate road irrespective of state boundaries — there is a simple remedy; and it cannot be assumed that it will not be readily applied if there be real occasion for it. That remedy does not rest in a denial to the state, in the absence of conflicting federal action, of its power to protect life and property within its borders, but it does lie in the exercise of the paramount authority of Congress in its control of interstate commerce to establish such regulations as in its judgment may be deemed appropriate and sufficient. Congress, when it pleases, may give the rule and make the standard to be observed on the interstate highway.” p. 292.

That same statement has in substance been made in many other decisions of this Court, a number of which are cited in the Atlantic Coast Line case, and all of them *792are today swept into the discard. In no one of all these previous cases was it more appropriate than here to call attention to the fact that Congress could when it pleased establish a uniform rule as to the length of trains. Congress knew about the Arizona law. It is common knowledge that the Interstate Commerce Committees of the House and the Senate keep in close and intimate touch with the affairs of railroads and other national means of transportation. Every year brings forth new legislation which goes through those Committees, much of it relating to safety. The attention of the members of Congress and of the Senate have been focused on the particular problem of the length of railroad trains. We cannot assume that they were ignorant of the commonly known fact that a long train might be more dangerous in some territories and on some particular types of railroad. The history of congressional consideration of this problem leaves little if any room to doubt that the choice of Congress to leave the state free in this field was a deliberate choice, which was taken with a full knowledge of the complexities of the problems and the probable need for diverse regulations in different localities. I am therefore compelled to reach the conclusion that today’s decision is the result of the belief of a majority of this Court that both the legislature of Arizona and the Congress made wrong policy decisions in permitting a law to stand which limits the length of railroad trains. I should at least give the Arizona statute the benefit of the same rule which this Court said should be applied in connection with state legislation under attack for violating the Fourteenth Amendment, that is, that legislative bodies have “a wide range of legislative discretion, . . . and their conclusions respecting the wisdom of their legislative acts are not reviewable by the courts.” Arizona Employers’ Liability Cases, 250 U. S. 400, 419.

*793When we finally get down to the gist of what the Court today actually decides, it is this: Even though more railroad employees will be injured by “slack action” movements on long trains than on short trains, there must be no regulation of this danger in the absence of “uniform regulations.” That means that no one can legislate against this danger except the Congress; and even though the Congress is perfectly content to leave the matter to the different state legislatures, this Court, on the ground of “lack of uniformity,” will require it to make an express avowal of that fact before it will permit a state to guard against that admitted danger.

We are not left in doubt as to why, as against the potential peril of injuries to employees, the Court tips the scales on the side of “uniformity.” For the evil it finds in a lack of uniformity is that it (1) delays interstate commerce, (2) increases its cost and (3) impairs its efficiency. All three of these boil down to the same thing, and that is that running shorter trains would increase the cost of railroad operations. The “burden” on commerce reduces itself to mere cost because there was no finding, and no evidence to support a finding, that by the expenditure of sufficient sums of'money, the railroads could not enable themselves to carry goods and passengers just as'quickly and efficiently with short trains as with long trains. Thus the conclusion that a requirement for long trains will “burden interstate commerce” is a mere euphemism for the statement that a requirement for long trains will increase the cost of railroad operations.

In the report of the Senate Committee, supra, attention was called to the fact that in 1935,6,351 railroad employees were injured while on duty, with a resulting loss of more than 200,000 working days, and that injuries to trainmen and enginemen increased more than 29% in 1936.5 Never*794theless, the Court’s action in requiring that money costs outweigh human values is sought to be buttressed by a reference to the express policy of Congress to promote an “economical national railroad system.” I cannot believe that if Congress had defined what it meant by “economical,” it would have required money to be saved at the expense of the personal safety of railway employees. Its whole history for the past 25 years belies such an interpretation of its language. Judicial opinions rather than legislative enactments have tended to emphasize costs. See Tiller v. Atlantic Coast Line R. Co., supra, 58-60. A different congressional attitude has been shown by the passage of numerous safety appliance provisions, a federal employees’ compensation act, abolition of the judicially created doctrine of assumption of risk and contributory negligence, and various other types of legislation. Unfortunately, the record shows, as pointed out in the Tiller case, that the courts have by narrow and restricted interpretation too frequently reduced the full scope of protection which Congress intended to provide.

This record in its entirety leaves me with no doubt whatever that many employees have been seriously injured and killed in the past, and that many more are likely to be so in the future, because of “slack, movement” in trains. Everyday knowledge as well as direct evidence presented at the various hearings, substantiates the report of the Senate Committee that the danger from slack movement is greater in long trains than in short trains. It may be that offsetting dangers are possible in the operation of short trains. The balancing of these probabilities, however, is not in my judgment a matter for judicial determination, but one which calls for legislative consideration. Representatives elected by the people to make their laws, rather than judges appointed to interpret those laws, can best determine the policies which govern the people. That at least is the basic principle on which our demo*795cratic society rests. I would affirm the judgment of the Supreme Court of Arizona.

Me. Justice Douglas,

dissenting.

I have expressed my doubts whether the courts should intervene in situations like the present and strike down state legislation on the grounds that it burdens interstate commerce. McCarroll v. Dixie Greyhound Lines, 309 U. S. 176, 183-189. My view has been that the courts should intervene only where the state legislation discriminated against interstate commerce or was out of harmony with laws which Congress had enacted, p. 184. It seems to me particularly appropriate that that course be followed here. For Congress has given the Interstate Commerce Commission broad powers of regulation over interstate carriers. The Commission is the national agency which has been entrusted with .the task of promoting a safe, adequate, efficient, and economical transportation service. It is the expert on this subject. It is in a position to police the field. And if its powers prove inadequate for the task, Congress, which has paramount authority in this field, can implement them.

But the Court has not taken that view. As a result the question presented is whether the total effect of Arizona’s train-limit as a safety measure is so slight as not to outweigh the national interest in keeping interstate commerce free from interferences which seriously impede or burden it. The voluminous evidence has been reviewed in the opinion of the Court and in the dissenting opinion of Mr. Justice Black. If I sat as a member of the Interstate Commerce Commission or of a legislative committee to decide whether Arizona’s train-limit law should be superseded by a federal regulation, the question would not be free from doubt for me. If we had before us the ruling of the Interstate Commerce Commission (In the Matter of Service Order No. 85, 256 I. C. C. 523, 534) that Ari*796zona’s train-limit law infringes “the national interest in maintaining the free flow of commerce under the present emergency war conditions,” I would accept its expert appraisal of the facts, assuming it had the authority to act. But that order is not before us. And the present case deals with a period of time which antedates the war emergency. Moreover, we are dealing here with state legislation in the field of safety where the propriety of local regulation has long been recognized. See Atlantic Coast Line R. Co. v. Georgia, 234 U. S. 280, 291, and cases collected in California v. Thompson, 313 U. S. 109, 113-114. Whether the question arises under the Commerce Clause or the Fourteenth Amendment, I think the legislation is entitled to a presumption of validity. If a State passed a law prohibiting the hauling of more than one freight car at a time, we would have a situation comparable in effect to a state law requiring all railroads within its borders to operate on narrow gauge tracks. The question is one of degree and calls for a close appraisal of the facts.1 I am not persuaded that the evidence adduced by the railroads overcomes the presumption of validity to which this train-limit law is entitled. For the reasons stated by Mr. Justice Black, Arizona’s train-limit law should stand as an allowable regulation enacted to protect the lives and limbs of the men who operate the trains.

Justice Powell

announced the judgment of the Court

and delivered an opinion, in which Justice White, Justice Blackmun, and Justice Stevens joined.

The question is whether an Iowa statute that prohibits the use of certain large trucks within the State unconstitutionally burdens interstate commerce.

I

Appellee Consolidated Freightways Corporation of Delaware (Consolidated) is one of the largest common carriers in *665the country. It offers service in 48 States under a certificate of public convenience and necessity issued by the Interstate Commerce Commission. Among other routes, Consolidated carries commodities through Iowa on Interstate 80, the principal east-west route linking New York, Chicago, and the west coast, and on Interstate 35, a major north-south route.

Consolidated mainly uses two kinds of trucks. One consists of a three-axle tractor pulling a 40-foot two-axle trailer. This unit, commonly called a single, or “semi,” is 55 feet in length overall. Such trucks have long been used on the Nation’s highways. Consolidated also uses a two-axle tractor pulling a single-axle trailer which, in turn, pulls a single-axle dolly and a second single-axle trailer. This combination, known as a double, or twin, is 65 feet long overall.1 Many trucking companies, including Consolidated, increasingly prefer to use doubles to ship certain kinds of commodities. Doubles have larger capacities, and the trailers can be detached and routed separately if necessary. Consolidated would like to use 65-foot doubles on many of its trips through Iowa.

The State of Iowa, however, by statute restricts the length of vehicles that may use its highways. Unlike all other States in the West and Midwest, App. 605, Iowa generally prohibits the use of 65-foot doubles within its borders. Instead, most truck combinations are restricted to 55 feet in length. Doubles,2 mobile homes,3 trucks carrying vehicles *666such as tractors and other farm equipment,4 and singles hauling livestock,5 are permitted to be as long as 60 feet. Notwithstanding these restrictions, Iowa’s statute permits cities abutting the state line by local ordinance to adopt the length limitations of the adjoining State. Iowa Code § 321.467 (7) (1979). Where a city has exercised this option, otherwise oversized trucks are permitted within the city limits and in nearby commercial zones. Ibid. 6

Iowa also provides for two other relevant exemptions. An Iowa truck manufacturer may obtain a permit to ship trucks that are as large as 70 feet. Iowa Code § 321E.10 (1979). Permits also are available to move oversized mobile homes, provided that the unit is to be moved from a point within Iowa or delivered for an Iowa resident. § 321E.28 (5).7

*667Because of Iowa’s statutory scheme, Consolidated cannot use its 65-foot doubles to move commodities through the State. Instead, the company must do one of four things: (i) use 55-foot singles; (ii) use 60-foot doubles; (iii) detach the trailers of a 65-foot double and shuttle each through the State separately; or (iv) divert 65-foot doubles around Iowa.

Dissatisfied with these options, Consolidated filed this suit in the District Court averring that Iowa’s statutory scheme unconstitutionally burdens interstate commerce.8 Iowa defended the law as a reasonable safety measure enacted pursuant to its police power. The State asserted that 65-foot doubles are more dangerous than 55-foot singles and, in any event, that the law promotes safety and reduces road wear within the State by diverting much truck traffic to other States.9

In a 14-day trial, both sides adduced evidence on safety, and on the burden on interstate commerce imposed by Iowa’s law. On the question of safety, the District Court found that the “evidence clearly establishes that the twin is as safe as the semi.’’ 475 F. Supp. 544, 549 (SD Iowa 1979). For that reason,

“there is no valid safety reason for barring twins from Iowa’s highways because of their configuration.

*668“The evidence convincingly, if not overwhelmingly, establishes that the 65 foot twin is as safe as, if not safer than, the 60 foot twin and the 55 foot semi. . . .

“Twins and semis have different characteristics. Twins are more maneuverable, are less sensitive to wind, and create less splash and spray. However, they are more likely than semis to jackknife or upset. They can be backed only for a short distance. The negative characteristics are not such that they render the twin less safe than semis overall. Semis are more stable but are more likely to hear end’ another vehicle.” Id., at 548-549.

In light of these findings, the District Court applied the standard we enunciated in Raymond Motor Transportation, Inc. v. Rice, 434 U. S. 429 (1978), and concluded that the state law impermissibly burdened interstate commerce:

“[T]he balance here must be struck in favor of the federal interests. The total effect of the law as a safety measure in reducing accidents and casualties is so slight and problematical that it does not outweigh the national interest in keeping interstate commerce free from interferences that seriously impede it.” 475 F. Supp., at 551 (emphasis in original).

The Court of Appeals for the Eighth Circuit affirmed. 612 F. 2d 1064 (1979). It accepted the District Court's finding that 65-foot doubles were as safe as 55-foot singles. Id., at 1069. Thus, the only apparent safety benefit to Iowa was that resulting from forcing large trucks to detour around the State, thereby reducing overall truck traffic on Iowa’s highways. The Court of Appeals noted that this was not a constitutionally permissible interest. Id., at 1070. It also commented that the several statutory exemptions identified above, such as those applicable to border cities and the shipment of livestock, suggested that the law in effect benefited Iowa *669residents at the expense of interstate traffic. Id., at 1070-1071. The combination of these exemptions weakened the presumption of validity normally accorded a state safety regulation. For these reasons, the Court of Appeals agreed with the District Court that the Iowa statute unconstitutionally burdened interstate commerce.

Iowa appealed, and we noted probable jurisdiction. 446 U. S. 950 (1980). We now affirm.

II

It is unnecessary to review in detail the evolution of the principles of Commerce Clause adjudicátion. The Clause is both a “prolific sourcfe] of national power and an equally prolific source of conflict with legislation of the state [s].” H. P. Hood & Sons, Inc. v. Du Mond, 336 U. S. 525, 534 (1949). The Clause permits Congress to legislate when it perceives that the national welfare is not furthered by the independent actions of the States. It is now well established, also, that the Clause itself is “a limitation upon state power even without congressional implementation.” Hunt v. Washington Apple Advertising Comm’n, 432 U. S. 333, 350 (1977). The Clause requires that some aspects of trade generally must remain free from interference by the States. When a State ventures excessively into the regulation of these aspects of commerce, it “trespasses upon national interests,” Great A&P Tea Co. v. Cottrell, 424 U. S. 366, 373 (1976), and the courts will hold the state regulation invalid under the Clause alone.

The Commerce Clause does not, of course, invalidate all state restrictions on commerce. It has long been recognized that, “in the absence of conflicting legislation by Congress, there is a residuum of power in the state to make laws governing matters of local concern which nevertheless in some measure affect interstate commerce or even, to some extent, regulate it.” Southern Pacific Co. v. Arizona, 325 U. S. 761, *670767 (1945). The extent of permissible state regulation is not always easy to measure. It may be said with confidence, however, that a State’s power to regulate commerce is never greater than in matters traditionally of local concern. Washington Apple Advertising Comm’n, supra, at 350. For ex-. ample, regulations that touch upon safety — especially highway safety — are those that “the Court has been most reluctant to invalidate.” Raymond, supra, at 443; accord, Railway Express Agency, Inc. v. New York, 336 U. S. 106, 109 (1949); South Carolina State Highway Dept. v. Barnwell Brothers, Inc., 303 U. S. 177, 187 (1938); Sproles v. Binford, 286 U. S. 374, 390 (1932); Hendrick v. Maryland, 235 U. S. 610, 622 (1915). Indeed, “if safety justifications are not illusory, the Court will not second-guess legislative judgment about their importance in comparison with related burdens on interstate commerce.” Raymond, supra, at 449 (Blackmun, J., concurring). Those who would challenge such bona fide safety regulations must overcome a “strong presumption of validity.” Bibb v. Navajo Freight Lines, Inc., 359 U. 520, 524 (1959).

But the incantation of a purpose to promote the public health or safety does not insulate a state law from Commerce Clause attack. Regulations designed for that salutary purpose nevertheless may further the purpose so marginally, and interfere with commerce so substantially, as to be invalid under the Commerce Clause. In the Court’s recent unanimous decision in Raymond, 10 we declined to “accept the State’s contention that the inquiry under the Commerce Clause is ended without a weighing of the asserted safety purpose against the degree of interference with interstate commerce.” 434 U. S., at 443. This “weighing” by a court requires — and indeed the constitutionality of the state regulation depends on — “a sensitive consideration of the weight *671and nature of the state regulatory concern in light of the extent of the burden imposed on the course of interstate commerce.” Id., at 441; accord, Pike v. Bruce Church, Inc., 397 U. S. 137, 142 (1970); Bibb, supra, at 525-530; Southern Pacific, supra, at 770.

Ill

Applying these general principles, we conclude that the Iowa truck-length limitations unconstitutionally burden interstate commerce.

In Raymond Motor Transportation, Inc. v. Rice, the Court held that a Wisconsin statute that precluded the use of 65-foot doubles violated the Commerce Clause. This case is Raymond revisited. Here, as in Raymond, the State failed to present any persuasive evidence that 65-foot doubles are less safe than 55-foot singles. Moreover, Iowa’s law is now out of step with the laws of all other Midwestern and Western States. Iowa thus substantially burdens the interstate flow of goods by truck. In the absence of congressional action to set uniform standards,11 some burdens associated with state safety regulations must be tolerated. But where, as here, the State’s safety interest, has. been.iouml to be inüsbry, and its regulations impair significantly the federal interest in efficient and safe interstate transportation, the state law cannot be harmonized with the Commerce Clause.12

A

Iowa made a more serious effort to support the safety-rationale of its .law than, did .Wisconsin in Raymond, but its *672effort was no more persuasive. As noted above, the District Court found that the “evidence clearly establishes that the twin is as safe as the semi.” The record supports this finding.

The trial focused on a comparison of the performance of the two kinds of trucks in various safety categories. The evidence showed, and the District Court found, that the 65-foot double was at least the equal of the 55-foot single in the ability to brake, turn, and maneuver. The double, because of its axle placement, produces less splash and spray in wet weather.13 And, because of its articulation in the middle, the double is less susceptible to dangerous “off-tracking,” 14 and to wind.

None of these findings is seriously disputed by Iowa. Indeed, the State points to only three ways in which the 55-foot single is even arguably superior: singles take less time to be passed and to clear intersections; they may back up for longer distances; and they are somewhat less likely to jackknife.

The first two of these characteristics are of limited relevance on modern interstate highways. As the District Court found, the negligible difference in the' time required to pass, and to cross intersections, is insignificant on 4-lane divided highways because passing does not require crossing into oncoming traffic lanes, Raymond, 434 U. S., at 444, and interstates have few, if any, intersections. The concern over backing capability also is insignificant because it seldom is necessary to back up *673on an interstate.15 In any event, no evidence suggested any difference in backing capability between the 60-foot doubles that Iowa permits and the 65-foot doubles that it bans. Similarly, although doubles tend to jackknife somewhat more than singles, 65-foot doubles actually are less likely to jackknife than 60-foot doubles.

Statistical studies supported the view that 65-foot doubles are at least as safe overall as 55-foot singles and 60-foot doubles. One such study, which the District Court credited, reviewed Consolidated’s comparative accident experience in 1978 with its own singles and doubles. Each kind of truck was driven 56 million miles on identical routes. The singles were involved in 100 accidents resulting in 27 injuries and one fatality. The 65-foot doubles were involved in 106 accidents resulting in 17 injuries and one fatality. Iowa’s expert statistician admitted that this study provided “moderately strong evidence” that singles have a higher injury rate than doubles. App. 488. Another study, prepared by the Iowa Department of Transportation at the request of the state legislature, concluded that “[s]ixty-five foot twin trailer combinations have not been shown by experiences in other states to be less safe than 60 foot twin trailer combinations or conventional tractor-semitrailers” (emphasis in original). Id., at 584. Numerous insurance company executives, and transportation officials from the Federal Government and various States, testified that 65-foot doubles were at least as safe as 55-foot singles. Iowa concedes that it can produce no study that establishes a statistically significant difference in safety between the 65-foot double and the kinds of vehicles the State permits. Brief for Appellants 28, 32. Nor, as the District Court noted, did Iowa present a single witness who testified that 65-foot doubles were more dangerous overall than the vehicles permitted under Iowa law. 475 F. Supp., at 549. *674In sum, although Iowa introduced more evidence on the question of safety than did Wisconsin in Raymond, the record as a whole was not more favorable to the State.16

B

Consolidated, meanwhile, demonstrated that Iowa’s law substantially burdens interstate commerce. Trucking companies that wish to continue to use 65-foot doubles must route them around Iowa or detach the trailers of the doubles and ship them through separately. Alternatively, trucking companies must use the smaller 55-foot singles or 60-foot doubles permitted under Iowa law. Each of these options engenders inefficiency and added expense. The record shows that Iowa’s law added about $12.6 million each year to the costs of trucking companies. Consolidated alone incurred about $2 million per year in increased costs.

In addition to increasing the costs of the trucking companies (and, indirectly, of the service to consumers), Iowa’s law may aggravate, rather than ^meliorate, the problem of highway accidents. Fifty-five foot singles carry less freight than 65-foot doubles. Either more small trucks must be used to carry the same quantity of goods through Iowa, or the same number of larger trucks must drive longer distances to bypass Iowa. In either case, as the District Court noted, *675the restriction requires more highway miles to be driven to transport the same quantity of goods. Other things being equal, accidents are proportional to distance traveled. See App. 604, 615.17 Thus, if 65-foot doubles are as safe as 55-foot singles, Iowa’s law tends to increase the number of accidents, and to shift the incidence of them from Iowa to other States.18

IV

Perhaps recognizing the weakness of the evidence supporting its safety argument, and the substantial burden on commerce that its regulations create, Iowa urges the Court simply to “defer” to the safety judgment of the State. It argues that the length of trucks is generally, although perhaps imprecisely, related to safety. The task of drawing a line is one that Iowa contends should be left to its legislature.

The Court normally does accord “special deference” to state highway safety regulations. Raymond, 434 U. S., at 444, n. 18. This traditional deference “derives in part from the assumption that where such regulations do not discriminate on their face against interstate commerce, their burden usually falls on local economic interests as well as other States’ economic interests, thus insuring that a State’s own political processes will serve as a check against unduly burdensome regulations.” Ibid. Less deference to the legislative judg*676ment is due, however, where the local regulation bears disproportionately on out-of-state residents and businesses. Such a disproportionate burden is apparent here. Iowa’s scheme, although generally banning large doubles from the State, nevertheless has several exemptions that secure to Iowans many of the benefits of large trucks while shunting to neighboring States many of the costs associated with their use.19

At the time of trial there were two particularly significant exemptions. First, singles hauling livestock or farm vehicles were permitted to be as long as 60 feet. Iowa Code §§ 321.457 (5), 321.457 (3) (1979). As the Court of Appeals noted, this provision undoubtedly was helpful to local interests. Cf. Raymond, supra, at 434 (exemption in Wisconsin for milk shippers). Second, cities abutting other States were permitted to enact local ordinances adopting the larger length limitation of the neighboring State. Iowa Code § 321.457 (7) (1979). This exemption offered the benefits of longer trucks to individuals and businesses in important border cities20 without burdening Iowa’s highways with interstate through traffic.21 Cf. Raymond, supra, at 446-447, and n. 24 (exemption in Wisconsin for shipments from local plants).22

*677The origin of the “border cities exemption” also suggests that Iowa’s statute may not have been designed to ban dangerous trucks, but rather to discourage interstate truck traffic. In 1974, the legislature passed a bill that would have permitted 65-foot doubles in the State. See n. 6, supra. Governor Ray vetoed the bill. He said:

“I find sympathy with those who are doing business in our state and whose enterprises could gain from increased cargo carrying ability by trucks. However, with this bill, the Legislature has pursued a course that would benefit only a few Iowa-based companies while providing a great advantage for out-of-state trucking firms and competitors at the expense of our Iowa citizens.” App. 626.23

After the veto, the “border cities exemption” was immediately enacted and signed by the Governor.

It is thus far from clear that Iowa was motivated primarily by a judgment that 65-foot doubles are less safe than 55-foot singles. Rather, Iowa seems to have hoped to limit the use of its highways by deflecting some through traffic.24 In the District Court and Court of Appeals, the State explicitly at-*678temped to justify the law by its claimed interest in keeping trucks out of Iowa. See n. 9 and accompanying text, supra. The Court of Appeals correctly concluded that a State cannot constitutionally promote its own parochial interests by requiring safe vehicles to detour around it. 612 F. 2d, at 1070.

y

In sum, the statutory exemptions, their history, and the arguments Iowa has advanced in support of its law in this litigation, all suggest that the deference traditionally accorded a State’s safety judgment is not warranted. See Raymond, supra, at 444, and n. 18, 446-447.25 The controlling factors thus are the findings of the District Court, accepted by the Court of Appeals, with respect to the relative safety of the types of trucks at issue, and the substantiality of the burden on interstate commerce.

Because Iowa has imposed this burden without any significant countervailing safety interest,26 its statute violates the *679Commerce Clause.27 The judgment of the Court of Appeals is affirmed.28

It is so ordered.

Justice Brennan,

with whom Justice Marshall joins, concurring in the judgment.

Iowa’s truck-length regulation challenged in this case is nearly identical to the Wisconsin regulation struck down in Raymond Motor Transportation, Inc. v. Rice, 434 U. S. 429 (1978), as in violation of the Commerce Clause. In my view the same Commerce Clause restrictions that dictated that holding also require invalidation of Iowa’s regulation insofar as it prohibits 65-foot doubles.

The reasoning bringing me to that conclusion does not require, however, that I engage in the debate between my Brothers Powell and Rehnquist over what the District Court record shows on the question whether 65-foot doubles are more dangerous than shorter trucks. With all respect, my Brothers ask and answer the wrong question.

For me, analysis of Commerce Clause challenges to state regulations must take into account three principles: (1) The courts are not empowered to second-guess the empirical judgments of lawmakers concerning the utility of legislation. *680(2) The burdens imposed on commerce must be balanced against the local benefits actually sought to be achieved by the State’s lawmakers, and not against those suggested after the fact by counsel. (3) Protectionist legislation is unconstitutional under the Commerce Clause, even if the burdens and benefits are related to safety rather than economics.

I

Both the opinion of my Brother Powell and the opinion of my Brother Rehnquist are predicated upon the supposition that the constitutionality of a state regulation is determined by the factual record created by the State’s lawyers in trial court. But that supposition cannot be correct, for it would make the constitutionality of state laws and regulations depend on the vagaries of litigation rather than on the judgments made by the State’s lawmakers.

In considering a Commerce Clause challenge to a state regulation, the judicial task is to balance the burden imposed on commerce against the local benefits sought to be achieved by the State’s lawmakers. See Pike v. Bruce Church, Inc., 397 U. S. 137, 142 (1970). In determining those benefits, a court should focus ultimately on the regulatory purposes identified by the lawmakers and on the evidence before or available to them that might have supported their judgment. See generally Minnesota v. Clover Leaf Creamery Co., 449 U. S. 456, 464, 473 (1981). Since the court must confine its analysis to the purposes the lawmakers had for maintaining the regulation, the only relevant evidence concerns whether the lawmakers could rationally have believed that the challenged regulation would foster those purposes. See Locomotive Firemen v. Chicago, R. I. & P. R. Co., 393 U. S. 129, 138-139 (1968); South Carolina State Highway Dept. v. Barnwell Bros., Inc., 303 U. S. 177, 192-193 (1938). It is not the function of the court to decide whether in fact the regulation promotes its intended purpose, so long as an examination of the evidence before or available to the lawmaker indicates *681that the regulation is not wholly irrational in light of its purposes. See Minnesota v. Clover Leaf Creamery Co., supra, at 469, 473.1

II

My Brothers Powell and REHjisrQuiST make the mistake of disregarding the intention of Iowa’s lawmakers and assuming that resolution of the case must hinge upon the argument offered by Iowa’s attorneys: that 65-foot doubles are more dangerous than shorter trucks. They then canvass the factual record and findings of the courts below and reach opposite conclusions as to whether the evidence adequately supports that empirical judgment. I repeat: my Brothers Powell and Rehnquist have asked and answered the wrong question. For although Iowa’s lawyers in this litigation have defended the truck-length regulation on the basis of the safety advantages of 55-foot singles and 60-foot doubles over 65-foot doubles, Iowa’s actual rationale for maintaining the regulation had nothing to do with these purported differences. Rather, Iowa sought to discourage interstate truck traffic on Iowa’s high*682ways.2 Thus, the safety advantages and disadvantages of the types and lengths of trucks involved in this case are irrelevant to the decision.3

*683My Brother Powell concedes that “[i]t is . . . far from clear that Iowa was motivated primarily by a judgment that 65-foot doubles are less safe than 55-foot singles. Rather, Iowa seems to have hoped to limit the use of its highways by deflecting some through trafile.” Ante, at 677. This conclusion is more than amply supported by the record and the legislative history of the Iowa regulation. The Iowa Legislature has consistently taken the position that size, weight, and speed restrictions on interstate trafile should be set in accordance with uniform national standards. The stated purpose was not to further safety but to achieve uniformity with other States. The Act setting the limitations challenged in *684this case, passed in 1947 and periodically amended since then, is entitled “An Act to promote uniformity with other states in the matter of limitations on the size, weight and speed of motor vehicles . . . 1947 Iowa Acts, ch. 177 (emphasis added). Following the proposals of the American Association of State Highway and Transportation Officials, the State has gradually increased the permissible length of trucks from 45 feet in 1947 to the present limit of 60 feet.

In 1974, the Iowa Legislature again voted to increase the permissible length of trucks to conform to uniform standards then in effect in most other States. This legislation, House Bill 671, would have increased the maximum length of twin trailer trucks operable in Iowa from 60 to 65 feet. But Governor Bay broke from prior state policy, and vetoed the legislation. The legislature did not override the veto, and the present regulation was thus maintained. In his veto,4 Governor Kay did not rest his decision on the conclusion that 55-foot singles and 60-foot doubles are any safer than 65-foot doubles, or on any other safety consideration inherent in the type or size of the trucks. Rather, his principal concern was that to allow 65-foot doubles would “basically ope[n] our state to literally thousands and thousands more trucks per year.” App. 628. This increase in interstate truck traffic would, in the Governor’s estimation, greatly increase highway maintenance costs, which are borne by the citizens of the State, id., at 628-629, and increase the number of accidents and fatalities within the State. Id., at 628. The legislative response was not to override the veto, but to accede to the Governor’s action, and in accord with his basic premise, to enact a “border cities exemption.” This permitted cities within border areas to allow 65-foot doubles while otherwise maintaining the 60-foot limit throughout the State to discourage interstate truck traffic.

*685Although the Court has stated that “[i]n no field has . . . deference to state regulation been greater than that of highway safety,” Raymond Motor Transportation, Inc. v. Rice, 434 U. S., at 443, it has declined to go so far as to presume that size restrictions are inherently tied to public safety. Id., at 444, n. 19. The Court has emphasized that the “strong presumption of validity” of size restrictions “cannot justify a court in closing its eyes to uncontroverted evidence of record,” ibid. — here the obvious fact that the safety characteristics of 65-foot doubles' did not provide the motivation for either legislators or Governor in maintaining the regulation.

Ill

Though my Brother Powell recognizes that the State’s actual purpose in maintaining the truck-length regulation was “to limit the use of its highways by deflecting some through traffic,” ante, at 677, he fails to recognize that this purpose, being protectionist in nature, is impermissible under the Commerce Clause.5 The Governor admitted that he blocked legislative efforts to raise the length of trucks because the change “would benefit only a few Iowa-based companies while providing a great advantage for out-of-state trucking firms and competitors at the expense of our Iowa citizens.” App. 626; see also id., at 185-186. Appellant Raymond Kassel, Director of the Iowa Department of Transportation, while admitting that the greater 65-foot length standard would be safer overall, defended the more restrictive regulations because of their benefits within Iowa:

“Q: Overall, there would be fewer miles of operation, fewer accidents and fewer fatalities?

“A: Yes, on the national scene.

“Q: Does it not concern the Iowa Department of *686Transportation that banning 65-foot twins causes more accidents, more injuries and more fatalities?

“A: Do you mean outside of our state border?

“Q: Overall.

“A: Our primary concern is the citizens of Iowa and our own highway system we operate in this state.” Id., at 281.

The regulation has had its predicted effect. As the District Court found:

“Iowa’s length restriction causes the trucks affected by the ban to travel more miles over more dangerous roads in other states which means a greater overall exposure to accidents and fatalities. More miles of highway are subjected to wear. More fuel is consumed and greater transportation costs are incurred.” 475 F. Supp. 544, 550 (SD Iowa 1979).

Iowa may not shunt off its fair share of the burden of maintaining interstate truck routes, nor may it create increased hazards on the highways of neighboring States in order to decrease the hazards on Iowa highways. Such an attempt has all the hallmarks of the “simple . . . protectionism” this Court has condemned in the economic area. Philadelphia v. New Jersey, 437 U. S. 617, 624 (1978). Just as a State’s attempt to avoid interstate competition in economic goods may damage the prosperity of the Nation as a whole, so Iowa’s attempt to deflect interstate truck traffic has been found to make the Nation’s highways as a whole more hazardous. That attempt should therefore be subject to “a virtually per se rule of invalidity.” Ibid.

This Court’s heightened deference to the judgments of state lawmakers in the field of safety, see ante, at 670, is largely attributable to a judicial disinclination to weigh the interests of safety against other societal interests, such as the economic interest in the free flow of commerce. Thus, “if safety justifications are not illusory, the Court will not second-*687guess legislative judgment about their importance in comparison with related burdens on interstate commerce.” Raymond Motor Transportation, Inc. v. Rice, supra, at 449 (Blackmun, J., concurring) (emphasis added). Here, the decision of Iowa’s lawmakers to promote Iowa’s safety and other interests at the direct expense of the safety and other interests of neighboring States merits no such deference. No special judicial acuity is demanded to perceive that this sort of parochial legislation violates the Commerce Clause. As Justice Cardozo has written, the Commerce Clause “was framed upon the theory that the peoples of the several states must sink or swim together, and that in the long run prosperity and salvation are in union and not division.” Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511, 523 (1935).

I therefore concur in the judgment.

Justice Rehnquist,

with whom The Chief Justice and Justice Stewart join, dissenting.

The result in this case suggests, to paraphrase Justice Jackson, that the only state truck-length limit “that is valid is one which this Court has not been able to get its hands on.” Jungersen v. Ostby & Barton Co., 335 U. S. 560, 572 (1949) (dissenting opinion). Although the plurality opinion and the opinion concurring in the judgment strike down Iowa’s law by different routes, I believe the analysis in both opinions oversteps our “limited authority to review state legislation under the commerce clause,” Locomotive Firemen v. Chicago, R. I. & P. R. Co., 393 U. S. 129, 136 (1968), and seriously intrudes upon the fundamental right of the States to pass laws to secure the safety of their citizens. Accordingly, I dissent.

I

It is necessary to elaborate somewhat on the facts as presented in the plurality opinion to appreciate fully what the Court does today. Iowa’s action in limiting the length of trucks which may travel on its highways is in no sense un*688usual. Every State in the Union regulates the length of vehicles permitted to use the public roads. Nor is Iowa a renegade in having length limits which operate to exclude the 65-foot doubles favored by Consolidated. These trucks are prohibited in other areas of the country as well, some 17 States and the District of Columbia, including all of New England and most of the Southeast.1 While pointing out that Consolidated carries commodities through Iowa on Interstate 80, “the principal east-west route linking New York, Chicago, and the west coast,” ante, at 665, the plurality neglects to note that both Pennsylvania and New Jersey, through which Interstate 80 runs before reaching New York, also ban 65-foot doubles. In short, the persistent effort in the plurality opinion to paint Iowa as an oddity standing alone to block commerce carried in 65-foot doubles is simply not supported by the facts.

Nor does the plurality adequately convey the extent to which the lower courts permitted the 65-foot doubles to operate in Iowa. Consolidated sought to have the 60-foot length limit declared an unconstitutional burden on commerce when applied to the seven Interstate Highways in Iowa2 and “access routes to and from Plaintiff’s terminals, and reasonable access from said Interstate Highways to facilities for food, fuel, repairs, or rest.” App. 10. The lower courts granted this relief, permitting the 65-foot doubles to travel off the Interstates as far as five miles for access to terminal and *689other facilities, or less if closer facilities were available. 475 F. Supp. 544, 553-554 (SD Iowa 1979). To the extent the plurality relies on characteristics of the Interstate Highways in rejecting Iowa’s asserted safety justifications, see ante, at 672-673, it fails to recognize the scope of the District Court order it upholds.

With these additions to the relevant facts, we can now examine the appropriate analysis to be applied.

II

Casual readers of this Court’s Commerce Clause decisions may be surprised, upon turning to the Constitution itself, to discover that the Clause in question simply provides that “The Congress shall have Power ... To regulate Commerce . . . among the several States.” Art. I, § 8, cl. 3. Although it is phrased in terms of an affirmative grant of power to the National Legislature, we have read the Commerce Clause as imposing some limitations on the States as well, even in the absence of any action by Congress. See Philadelphia v. New Jersey, 437 U. S. 617, 623 (1978). The Court has hastened to emphasize, however, that the negative implication it has discerned in the Commerce Clause does not invalidate state legislation simply because the legislation burdens interstate commerce.

“In determining whether the state has imposed an undue burden on interstate commerce, it must be borne in mind that the Constitution when 'conferring upon Congress the regulation of commerce, . . . never intended to cut the States off from legislating on all subjects relating to the health, life, and safety of their citizens, though the legislation might indirectly affect the commerce of the country.’ ” Huron Portland Cement Co. v. Detroit, 362 U. S. 440, 443-444 (1960) (quoting Sherlock v. Ailing, 93 U. S. 99, 103 (1876)).

See Raymond Motor Transportation, Inc. v. Rice, 434 U. S. *690429, 440 (1978); Southern Pacific Co. v. Arizona, 325 U. S. 761, 767 (1945). The Commerce Clause is, after all, a grant of authority to Congress, not to the courts. Although the Court when it interprets the “dormant” aspect of the Commerce Clause will invalidate unwarranted state intrusion, such action is a far cry from simply undertaking to regulate when Congress has not because we believe such regulation would facilitate interstate commerce. Cf. Northwest Airlines, Inc. v. Minnesota, 322 U. S. 292, 302 (1944) (Black, J., concurring) (“The Constitution gives [Congress] the power to regulate commerce among the states, and until it acts I think we should enter the field with extreme caution”).

It is also well established that “the Court has been most reluctant to invalidate under the Commerce Clause ‘state legislation in the field of safety where the propriety of local regulation has long been recognized.’ ” Raymond, supra, at 443 (quoting Pike v. Bruce Church, Inc., 397 U. S. 137, 143 (1970)). The propriety of state regulation of the use of public highways was explicitly recognized in Morris v. Duby, 274 U. S. 135, 143 (1927), where Chief Justice Taft wrote that “[i]n the absence of national legislation especially covering the subject of interstate commerce, the State may rightfully prescribe uniform regulations adapted to promote safety upon its highways and the conservation of their use, applicable alike to vehicles moving in interstate commerce and those of its own citizens.” The Court very recently reaffirmed the longstanding view that “[i]n no field has . . . deference to state regulation been greater than that of highway safety.” Raymond, supra, at 443. See Railway Express Agency, Inc. v. New York, 336 U. S. 106, 111 (1949); South Carolina State Highway Dept. v. Barnwell Brothers, Inc., 303 U. S. 177, 187 (1938); Sproles v. Binford, 286 U. S. 374, 390 (1032); Hendrick v. Maryland, 235 U. S. 610, 622 (1915). Those challenging a highway safety regulation must overcome a “strong presumption of validity,” Bibb v. Navajo Freight Lines, Inc., 359 U. S. 520, 524 (1959), particularly *691when, as here, Congress has not acted in the area and the claim is that “the bare possession of power by Congress” invalidates the state legislation. Barnwell Brothers, supra, at 187.3

A determination that a state law is a rational safety measure does not end the Commerce Clause inquiry. A “sensitive consideration” of the safety purpose in relation to the burden on commerce is required. Raymond, supra, at 441. When engaging in such a consideration the Court does not directly compare safety benefits to commerce costs and strike down the legislation if the latter can be said in some vague sense to “outweigh” the former. Such an approach would make an empty gesture of the strong presumption of validity accorded state safety measures, particularly those governing highways. It would also arrogate to this Court functions of forming public policy, functions which, in the absence of congressional action, were left by the Framers of the Constitution to state legislatures. “[I]n reviewing a state highway regulation where Congress has not acted, a court is not called upon, as are state legislatures, to determine what, in its judgment, is the most suitable restriction to be applied of those that are possible, or to choose that one which in its opinion is best adapted to all the diverse interests affected.” Barnwell Brothers, supra, at 190. See Locomotive Firemen, 393 U. S., at 138 (“[T]he question'of safety in the circumstances of this case is essentially a matter of public policy, and public policy can, under our constitutional system, be fixed only by the people acting through their elected representatives”); Bibb, supra, at 524 (“If there are alternative ways of solving a problem, we do not sit to determine which of them is best *692suited to achieve a valid state objective. Policy decisions are for the state legislature”)- These admonitions are peculiarly apt when, as here, the question involves the difficult comparison of financial losses and “the loss of lives and limbs of workers and people using the highways.” Locomotive Firemen, supra, at 140.4

The purpose of the “sensitive consideration” referred to above is rather to determine if the asserted safety justification, although rational, is merely a pretext for discrimination against interstate commerce. We will conclude that it is if the safety benefits from the regulation are demonstrably trivial while the burden on commerce is great. Thus the Court in Bibb stated that the “strong presumption of validity” accorded highway safety measures could be overcome only when the safety benefits were “slight or problematical,” 359 U. S., at 524. See Raymond, 434 U. S., at 449 (Blackmun, J., concurring) (“[I]f safety justifications are not illusory, the Court will not second-guess legislative judgment about their importance in comparison with related burdens on interstate commerce”). The nature of the inquiry is perhaps best illustrated by examining those cases in which state safety laws have been struck down on Commerce Clause grounds. In Southern Pacific a law regulating train lengths was viewed by the Court as having “at most slight and dubious advantage, if any, over unregulated train lengths,” 325 U. S., at 779; the lower courts concluded the law actually tended to increase the number of accidents by increasing the number of trains, id., at 777. In Bibb the contoured mudguards re*693quired by Illinois, alone among the States, had no safety advantages over conventional mudguards and, as in Southern Pacific, actually increased hazards. 359 U. S., at 525; id., at 530 (Harlan, J., concurring). In Great A&P Tea Co. v. Cottrell, 424 U. S. 366, 375-376 (1976), the Court struck down a Mississippi “reciprocity clause” concerning milk inspection because it “disserve[d] rather than promote[d] any higher Mississippi milk quality standards.” The cases thus demonstrate that the safety benefits of a state law must be slight indeed before it will be struck down under the dormant Commerce Clause.

Ill

Iowa defends its statute as a highway safety regulation. There can be no doubt that the challenged statute is a valid highway safety regulation and thus entitled to the strongest presumption of validity against Commerce Clause challenges. As noted, all 50 States regulate the length of trucks which may use their highways. Cf. West Coast Hotel Co. v. Parrish, 300 U. S. 379, 399 (1937) (“The adoption of similar requirements by many States evidences a deepseated conviction both as to the presence of the evil and as to the means adapted to check it”). The American Association of State Highway and Transportation Officials (AASHTO) has consistently recommended length as well as other limits on vehicles.5 The Iowa Supreme Court has long viewed the provision in question as intended to promote highway safety, see Wood Brothers Thresher Co. v. Eicher, 231 Iowa 550, 559-560, 1 N. W. 2d 655, 660 (1942); State v. United-Buckingham Freight Lines, Inc., 211 N. W. 2d 288, 290 (1973), and “[t]his Court has also had occasion to point out that the sizes and weights of automobiles have an important relation *694to the safe and convenient use of the highways, which are matters of state control.” Maurer v. Hamilton, 309 U. S. 598, 609 (1940). There can also be no question that the particular limit chosen by Iowa — 60 feet — is rationally related to Iowa’s safety objective. Most truck limits are between 55 and 65 feet, see App. 645, and Iowa’s choice is thus well within the widely accepted range.

Iowa adduced evidence supporting the relation between vehicle length and highway safety. The evidence indicated that longer vehicles take greater time to be passed, thereby increasing the risks of accidents, particularly during the inclement weather not uncommon in Iowa. Id., at 504-505. The 65-foot vehicle exposes a passing driver to visibility-impairing splash and spray during bad weather for a longer period than do the shorter trucks permitted in Iowa.6 Longer trucks are more likely to clog intersections, id., at 457, and although there are no intersections on the Interstate Highways, the order below went beyond the highways themselves and the concerns about greater length at intersections would arise “[a]t every trip origin, every trip destination, every intermediate stop for picking up trailers, reconfiguring loads, change of drivers, eating, refueling — every intermediate stop would generate this type of situation.” Ibid. The Chief of the Division of *695Patrol in the Iowa Department of Public Safety testified that longer vehicles pose greater problems at the scene of an accident. For example, trucks involved in accidents often must be unloaded at the scene, id., at 400, which would take longer the bigger the load.

In rebuttal of Consolidated’s evidence on the relative safety of 65-foot doubles to trucks permitted oh Iowa’s highways, Iowa introduced evidence that doubles are more likely than singles to jackknife or upset, id., at 507. The District Court concluded that this was so and that singles are more stable than doubles. 475 F. Supp., at 549.7 Iowa also introduced evidence from Consolidated’s own records showing that Consolidated’s overall accident rate for doubles exceeded that of semis for three of the last four years, App. 668-675, and that some of Consolidated’s own drivers expressed a preference for the handling characteristics of singles over doubles. 475 F. Supp., at 549.

In addition Iowa elicited evidence undermining the probative value of Consolidated’s evidence. For example, Iowa established that the more experienced drivers tended to drive doubles, because they have seniority and driving doubles is a higher paying job than driving singles. Since the leading cause of accidents was driver error, Consolidated’s evidence of the relative safety record of doubles may have been based in large part not on the relative safety of the vehicles themselves but on the experience of the drivers. App. 27-28. Although the District Court, the Court of Appeals, and the plurality all fail to recognize the fact, Iowa also negated much of Consolidated’s evidence by establishing that it considered the relative safety of doubles to singles, and not the question of length alone. Consolidated introduced much *696evidence that its doubles were as safe as singles. See, e. g., id., at 23, 32-36, 45, 89, 153, 289, 304, 586, 609. Such evidence is beside the point. The trucks which Consolidated wants to run in Iowa are prohibited because of their length, not their configuration. Doubles are allowed in Iowa, up to a length of 60 feet, and Consolidated in fact operates 60-foot doubles in Iowa. Consolidated’s experts were often forced to admit that they could draw no conclusions about the relative safety of 65-foot doubles and 60-foot doubles, as opposed to doubles and singles. See, e. g., id., at 26, 53, 308. Conclusions that the double configuration is as safe as the single do not at all mean the 65-foot double is as safe as the 60-foot double, or that length is not relevant to vehicle safety. For example, one of Consolidated’s experts testified that doubles “off track” better than singles, because of their axle placement, but conceded on cross-examination that a 60-foot double would off-track better than a 65-foot double. Id., at 97, 107. In sum, there was sufficient evidence presented at trial to support the legislative determination that length is related to safety, and nothing in Consolidated’s evidence undermines this conclusion.

The District Court approached the case as if the question were whether Consolidated’s 65-foot trucks were as safe as others permitted on Iowa highways, and the Court of Appeals as if its task were to determine if the District Court’s factual findings in this regard were “clearly erroneous.” 612 F. 2d, at 1069. The question, however, is whether the Iowa Legislature has acted rationally in regulating vehicle lengths and whether the safety benefits from this regulation are more than slight or problematical. “The classification of the traffic for the purposes of regulation ... is a legislative, not a judicial, function. Its merits are not to be weighed in the judicial balance and the classification rejected merely because the weight of the evidence in court appears to favor a different standard.” Clark v. Paul Gray, Inc., 306 U. S. 583, 594 (1939). “Since the adoption of one weight or width regula*697tion, rather than another, is a legislative and not a judicial choice, its constitutionality is not to be determined by weighing in the judicial scales the merits of the legislative choice and rejecting it if the weight of evidence presented in court appears to favor a different standard.” Barnwell Brothers, 303 U. S., at 191.8

The answering of the relevant question is not appreciably advanced by comparing trucks slightly over the length limit with those at the length limit. It is emphatically not our task to balance any incremental safety benefits from prohibiting 65-foot doubles as opposed to 60-foot doubles against the burden on interstate commerce. Lines drawn for safety purposes will rarely pass muster if the question is whether a slight increment can be permitted without sacrificing safety. As Justice Holmes put it:

“When a legal distinction is determined, as no one doubts that it may be, between night and day, childhood *698and maturity, or any other extremes, a point has to be fixed or a line has to be drawn, or gradually picked out by successive decisions, to mark where the change takes place. Looked at by itself without regard to the necessity behind it the line or point seems arbitrary. It might as well or nearly as well be a little more to one side or the other. But when it is seen that a line or point there must be, and that there is no mathematical or logical way of fixing it precisely, the decision of the legislature must be accepted unless we can say that it is very wide of any reasonable mark.” Louisville Gas & Electric Co. v. Coleman, 277 U. S. 32, 41 (1938) (dissenting opinion).

The question is rather whether it can be said.that the benefits flowing to Iowa from a rational truck-length limitation are “slight or problematical.” See Bibb, 359 U. S., at 524. The particular line chosen by Iowa — 60 feet — is relevant only to the question whether the limit is a rational one. Once a court determines that it is, it considers the overall safety benefits from the regulation against burdens on interstate commerce, and not any marginal benefits from the scheme the State established as opposed to that the plaintiffs desire. See Southern Pacific, 325 U. S., at 779 (train-length law struck down because it “affords at most slight and dubious advantage, if any, over unregulated train lengths”) (emphasis supplied) ; Barnwell Brothers, supra, at 190-192.

The difficulties with the contrary approach are patent. While it may be clear that there are substantial safety benefits from a 55-foot truck as compared to a 105-foot truck, these benefits may not be discernible in 5-foot jumps. Appellee’s approach would permit what could not be accomplished in one lawsuit to be done in 10 separate suits, each challenging an additional five feet.

Any direct balancing of marginal safety benefits against burdens on commerce would make the burdens on commerce the sole significant factor, and make likely the odd result that *699similar state laws enacted for identical safety reasons might violate the Commerce Clause in one part of the country but not another. For example, Mississippi and Georgia prohibit trucks over 55 feet. Since doubles are not operated in the Southeast, the demonstrable burden on commerce may not be sufficient to strike down these laws, while Consolidated maintains that it is in this case, even though the doubles here are given an additional five feet. On the other hand, if Consolidated were to win this case it could shift its 65-foot doubles to routes leading into Mississippi or Georgia (both States border States in which 65-foot trucks are permitted) and claim the same constitutional violation it claims in this case. Consolidated Freightways, and not this Court, would become the final arbiter of the Commerce Clause.

It must be emphasized that there is nothing in the laws of nature which make 65-foot doubles an obvious norm. Consolidated operates 65-foot doubles on many of its routes simply because that is the largest size permitted in many States through which Consolidated travels. App. 92, 240, 364-365. Doubles can and do come in smaller sizes; indeed, when Iowa adopted the present 60-foot limit in 1963, it was in accord with AASHTO recommendations. Striking down Iowa’s law because Consolidated has made a voluntary business decision to employ 65-foot doubles, a decision based on the actions of other state legislatures,-would essentially be compelling Iowa to yield to the policy choices of neighboring States. Under our constitutional scheme, however, there is only one legislative body which can pre-empt the rational policy determination of the Iowa Legislature and that is Congress. Forcing Iowa to yield to the policy choices of neighboring States perverts the primary purpose of the Commerce Clause, that of vesting power to regulate interstate commerce in Congress, where all the States are represented. In Barnwell Brothers, the Court upheld a South Carolina width limit of 90 inches even though “all other states permit a width of 96 inches, which is the standard width of trucks engaged in interstate *700commerce.” 303 U. S., at 184. Then Justice Stone, writing for the Court, stressed:

“The fact that many states have adopted a different standard is not persuasive. . . . The legislature, being free to exercise its own judgment, is not bound by that of other legislatures. It would hardy be contended that if all the states had adopted a single standard none, in the light of its own experience and in the exercise Of its judgment upon all the complex elements which enter into the problem, could change it.” Id., at 195-196.

See also Sproles, 286 U. S., at 390. Nor is Iowa’s policy preempted by Consolidated’s decision to invest in 65-foot trucks, particularly since this was done when Iowa’s 60-foot limit was on the books. Cf. id., at 390-391.9

The Court of Appeals felt compelled to reach the result it did in light of our decision in Raymond and the plurality agrees that “[t]his case is Raymond revisited,” ante, at 671.10 Raymond, however, does not control this case. The Court in Raymond emphasized that “[o]ur holding is a narrow one, for we do not decide whether laws of other States restricting the operation of trucks over 55 feet long, or of double-trailer trucks, would be upheld if the evidence produced on the safety *701issue were not so overwhelmingly one-sided as in this case.” 434 U. S., at 447.11 The Raymond Court repeatedly stressed that the State “made no effort to contradict . . . evidence of comparative safety with evidence of its own,” id., at 437, that •the trucking companies’ evidence was “uncontroverted,” id., at 445, n. 19, and that the State “virtually defaulted in its defense of the regulations as a safety measure,” id., at 444. By contrast, both the District Court and the Court of Appeals recognized that Iowa “made an all out effort” and “zealously presented arguments” on its safety case. 475 F. Supp., at 548; 612 F. 2d, at 1067-1068. As noted, Iowa has adduced evidence sufficient to support its safety claim and has rebutted much of the evidence submitted by Consolidated.

Furthermore, the exception to the Wisconsin prohibition which the Court specifically noted in Raymond finds no parallel in this case. The exception in Raymond permitted oversized vehicles to travel from plant to plant in Wisconsin or between a Wisconsin plant and the border. 434 U. S., at 446, and n. 24. As the Court noted, this discriminated on its face between Wisconsin industries and the industries of other States. The border-cities exception to the Iowa length limit does not. Iowa shippers in cities with border-city ordinances may use longer vehicles in interstate commerce, but interstate shippers coming into such cities may do so as well. Cities without border-city ordinances may neither export nor import on oversized vehicles. Nor can the border-cities exception be “[v]iewed realistically,” as was the Wisconsin exception, to “be the product of compromise between forces within the State that seek to retain the State’s general truck-length limit, and industries within the State that complain that the general limit is unduly burdensome.” Raymond, 434 U. S., at 447. The Wisconsin exception was available to all Wisconsin industries wanting to ship out of State from Wis-*702cousin plants. The border-cities exception is of much narrower applicability: only 5 of Iowa’s 16 largest cities and only 8 cities in all permit oversized trucks under the border-cities exception. The population of the eight cities with border-city ordinances is only 13 percent of the population of the State.12

My Brother Brennan argues that the Court should consider only the purpose the Iowa legislators actually sought to achieve by the length limit, and not the purposes advanced by Iowa’s lawyers in defense of the statute. This argument calls to mind what was said of the Roman Legions: that they may have lost battles, but they never lost a war, since they never let a war end until they had won it. The argument has been consistently rejected by the Court in other contexts, compare, e. g., United, States Railroad Retirement Board v. Fritz, 449 U. S. 166, 187-188 (1980), with id., at 187-188 (Brennan, J., dissenting), and Michael M. v. Superior Court of Sonoma County, ante, at 469-470 (plurality opinion), with ante, at 494-496 (Brennan, J., dissenting), and Justice Brennan can cite no authority for the proposition that possible legislative purposes suggested by a State’s lawyers should not be considered in Commerce Clause cases. The problems with a view such as that advanced in the opinion concurring in the judgment are apparent. To name just a few, it assumes that individual legislators are motivated by one discernible “actual” purpose, and ignores the fact that different legislators may vote for a single piece of legislation for widely *703different reasons. See Michael M., ante, at 469-470; Arlington Heights v. Metropolitan Housing Dev. Corp., 429 U. S. 252, 265 (1977); McGinnis v. Royster, 410 U. S. 263, 276-277 (1973). How, for example, would a court adhering to the views expressed in the opinion concurring in the judgment approach a statute, the legislative history of which indicated that 10 votes were based on safety considerations, 10 votes were based on protectionism, and the statute passed by a vote of 40-20? What would the actual purpose of the legislature have been in that case? This Court has wisely “never insisted that a legislative body articulate its reasons for enacting a statute.” Fritz, supra, at 461.13

*704Both the plurality and the concurrence attach great significance to the Governor’s veto of a bill passed by the Iowa Legislature permitting 65-foot doubles. Whatever *705views one may have about the significance of legislative motives, it must be emphasized that the law which the Court strikes down today was not passed to achieve the protectionist goals the plurality and the concurrence ascribe to the Governor. Iowa’s 60-foot length limit was established in 1963, at a time when very few States permitted 65-foot doubles. See App. to Reply Brief for Appellants la, 2a. Striking down legislation on the basis of asserted legislative motives is dubious enough, but the plurality and concurrence strike down the legislation involved in this case because of asserted impermissible motives for not enacting other legislation, motives which could not possibly have been present when the legislation under challenge here was considered and passed. Such action is, so far as I am aware, unprecedented in this Court’s history.

Furthermore, the effort in both the plurality and the concurrence to portray the legislation involved here as protectionist is in error. Whenever a State enacts more stringent safety measures than its neighbors, in an area which affects commerce, the safety law will have the incidental effect of deflecting interstate commerce to the neighboring States. Indeed, the safety and protectionist motives cannot be separated: The whole purpose of safety regulation of vehicles *706is to protect the State from unsafe vehicles. If a neighboring State chooses not to protect its citizens from the danger discerned by the enacting State, that is its business, but the enacting State should not be penalized when the vehicles it considers unsafe travel through the neighboring State.

The other States with truck-length limits that exclude Consolidated's 65-foot doubles would not at all be paranoid in assuming that they might be next on Consolidated’s “hit list.” 14 The true problem with today's decision is that it gives no guidance whatsoever to these States as to whether their laws are valid or how to defend them. For that matter, the decision gives no guidance to Consolidated or other trucking firms either. Perhaps, after all is said and done, the Court today neither says nor does very much at all. We know only that Iowa’s law is invalid and that the jurisprudence of the “negative side” of the Commerce Clause remains hopelessly confused.

Mr. Justice Clark

delivered the opinion of the Court.

This appeal challenges the constitutional validity of two sections of an ordinance of the City of Madison, Wisconsin, regulating the sale of milk and milk products within the municipality’s jurisdiction. One section in issue makes it unlawful to sell any milk as pasteurized unless it has been processed and bottled at an approved pasteurization plant within a radius of five miles from the central square of Madison.1 Another section, which prohibits the sale of milk, or the importation, receipt or storage of milk for sale, in Madison unless from a source of supply possessing a permit issued after inspection by Madison officials, is attacked insofar as it expressly relieves municipal authorities from any duty to inspect farms *351located beyond twenty-five miles from the center of the city.2

Appellant is an Illinois corporation engaged in distributing milk and milk products in Illinois and Wisconsin. It contended below, as it does here, that both the five-mile limit on pasteurization plants and the twenty-five-mile limit on sources of milk violate the Commerce Clause and the Fourteenth Amendment to the Federal Constitution. The Supreme Court of Wisconsin upheld the five-mile limit on pasteurization.3 As to the twenty-five-mile limitation the court ordered the complaint dismissed for want of a justiciable controversy. 257 Wis. 308, 43 N. W. 2d 480 (1950). This appeal, contesting both rulings, invokes the jurisdiction of this Court under 28 U. S. C. § 1257 (2).

The City of Madison is the county seat of Dane County. Within the county are some 5,600 dairy farms with total *352raw milk production in excess of 600,000,000 pounds annually and more than ten times the requirements of Madison. Aside from the milk supplied to Madison, fluid milk produced in the county moves in large quantities to Chicago and more distant consuming areas, and the remainder is used in making cheese, butter and other products. At the time of trial the Madison milkshed was not of “Grade A” quality by the standards recommended by the United States Public Health Service, and no milk labeled “Grade A” was distributed in Madison.

The area defined by the ordinance with respect to milk sources encompasses practically all of Dane County and includes some 500 farms which supply milk for Madison. Within the five-mile area for pasteurization are plants of five processors, only three of which are engaged in the general wholesale and retail trade in Madison. Inspection of these farms and plants is scheduled once every thirty days and is performed by two municipal inspectors, one of whom is full-time. The courts below found that the ordinance in question promotes convenient, economical and efficient plant inspection.

Appellant purchases and gathers milk from approximately 950 farms in northern Illinois and southern Wisconsin, none being within twenty-five miles of Madison. Its pasteurization plants are located at Chemung and Huntley, Illinois, about 65 and 85 miles respectively from Madison. Appellant was denied a license to sell its products within Madison solely because its pasteurization plants were more than five miles away.

It is conceded that the milk which appellant seeks to sell in Madison is supplied from farms and processed in plants licensed and inspected by public health authorities of Chicago, and is labeled “Grade A” under the Chicago ordinance which adopts the rating standards recommended by the United States Public Health Serv*353ice. Both the Chicago and Madison ordinances, though not the sections of the latter here in issue, are largely patterned after the Model Milk Ordinance of the Public Health Service. However, Madison contends and we assume that in some particulars its ordinance is more rigorous than that of Chicago.

Upon these facts we find it necessary to determine only the issue raised under the Commerce Clause, for we agree with appellant that the ordinance imposes an undue burden on interstate commerce.

This is not an instance in which an enactment falls because of federal legislation which, as a proper exercise of paramount national power over commerce, excludes measures which might otherwise be within the police power of the states. See Currin v. Wallace, 306 U. S. 1, 12-13 (1939). There is no pertinent national regulation by the Congress, and statutes enacted for the District of Columbia indicate that Congress has recognized- the appropriateness of local regulation of the sale of fluid milk. D. C. Code, 1940, §§ 33-301 et seq. It is not contended, however, that Congress has authorized the regulation before us.

Nor can there be objection to the avowed purpose of this enactment. We assume that difficulties in sanitary regulation of milk and milk products originating in remote areas may present a situation in which “upon a consideration of all the relévant facts and circumstances it appears that the matter is one which may appropriately be regulated in the interest of the safety, health and well-being of local communities . . . Parker v. Brown, 317 U. S. 341, 362-363 (1943); see H. P. Hood & Sons v. Du Mond, 336 U. S. 525, 531-532 (1949). We also assume that since Congress has not spoken to the contrary, the subject matter of the ordinance lies within the sphere of state regulation even though interstate com*354merce may be affected. Milk Control Board v. Eisenberg Farm Products, 306 U. S. 346 (1939); see Baldwin v. Seelig, Inc., 294 U. S. 511, 524 (1935).

But this regulation, like the provision invalidated in Baldwin v. Seelig, Inc., supra, in practical effect excludes from distribution in Madison wholesome milk produced and pasteurized in Illinois. “The importer . . . may keep his milk or drink it, but sell it he may not.” Id., at 521. In thus erecting an economic barrier protecting a major local industry against competition from without the State, Madison plainly discriminates against interstate commerce.4 This it cannot do, even in the exercise of its unquestioned power to protect the health and safety of its people, if reasonable nondiscriminatory alternatives, adequate to conserve legitimate local interests, are available. Cf. Baldwin v. Seelig, Inc., supra, at 524; Minnesota v. Barber, 136 U. S. 313, 328 (1890). A different view, that the ordinance is valid simply because it professes to be a health measure, would mean that the Commerce Clause of itself imposes no limitations on state action other than those laid down by the Due Process Clause, save for the rare instance where a state artlessly discloses an avowed purpose to discriminate against interstate goods. Cf. H. P. Hood & Sons v. Du Mond, supra. Our issue then is whether the discrimination inherent, in the Madison ordinance can be justified in view of the character of the local interests and the available methods of protecting them. Cf. Union Brokerage Co. v. Jensen, 322 U. S. 202, 211 (1944).

It appears that reasonable and adequate alternatives are available. If the City of Madison prefers to rely upon its own officials for inspection of distant milk *355sources, such inspection is readily open to it without hardship for it could charge the actual and reasonable cost of such inspection to the importing producers and processors. Cf. Sprout v. City of South Bend, 277 U. S. 163, 169 (1928); see Miller v. Williams, 12 F. Supp. 236, 242, 244 (D. Md. 1935). Moreover, appellee Health Commissioner of Madison testified that as proponent of the local milk ordinance he had submitted the provisions here in controversy and an alternative proposal based on § 11 of the Model Milk Ordinance recommended by the United States Public Health Service. The model provision imposes no geographical limitation on location of milk sources and processing plants but excludes from the municipality milk not produced and pasteurized conformably to standards as high as those enforced by the receiving city.5 In implementing such an ordinance, the importing city obtains milk ratings based on uniform standards and established by health authorities in the jurisdiction where production and processing occur. The receiving city may *356determine the extent of enforcement of sanitary standards in the exporting area by verifying the accuracy of safety ratings of specific plants or of the milkshed in the distant jurisdiction through the United States Public Health Service, which routinely and on request spot checks the local ratings. The Commissioner testified that Madison consumers “would be safeguarded adequately” under either proposal and that he had expressed no preference. The milk sanitarian of the Wisconsin State Board of Health testified that the State Health Department recommends the adoption of a provision based on the Model Ordinance. Both officials agreed that a local health officer would be justified in relying upon the evaluation by the Public Health Service of enforcement conditions in remote producing areas.

To permit Madison to adopt a regulation not essential for the protection of local health interests and placing a discriminatory burden on interstate commerce would invite a multiplication of preferential trade areas destructive of the very purpose of the Commerce Clause. Under the circumstances here presented, the regulation must yield to the principle that “one state in its dealings with another may not place itself in a position of economic isolation.” Baldwin v. Seelig, Inc., supra, at 527.

For these reasons we conclude that the judgment below sustaining the five-mile provision as to pasteurization must be reversed.

The Supreme Court of Wisconsin thought it unnecessary to pass upon the validity of the twenty-five-mile limitation, apparently in part for the reason that this issue was made academic by its decision upholding the five-mile section. In view of our conclusion as to the latter provision, a determination of appellant's contention as to the other section is now necessary. As to this *357issue, therefore, we vacate the judgment below and remand for further proceedings not inconsistent with the principles announced in this opinion.

It is so ordered.

Mr. Justice Black,

with whom Mr. Justice Douglas and Mr. Justice Minton concur, dissenting.

Today’s holding invalidates § 7.21 of the Madison, Wisconsin, ordinance on the following reasoning: (1) the section excludes wholesome milk coming from Illinois; (2) this imposes a discriminatory burden on interstate commerce; (3) such a burden cannot be imposed where, as here, there are reasonable, nondiscriminatory and adequate alternatives available. I disagree with the Court’s premises, reasoning, and judgment.

(1) This ordinance does not exclude wholesome milk coming from Illinois or anywhere else. It does require that all milk sold in Madison must be pasteurized within five miles of the center of the city. But there was no finding in the state courts, nor evidence to justify a finding there or here, that appellant, Dean Milk Company, is unable to have its milk pasteurized within the defined geographical area. As a practical matter, so far as the record shows, Dean can easily comply with the ordinance whenever it wants to. Therefore, Dean’s personal preference to pasteurize in Illinois, not the ordinance, keeps Dean’s milk out of Madison.

(2) Characterization of § 7.21 as a “discriminatory burden” on interstate commerce is merely a statement of the Court’s result, which I think incorrect. The section does prohibit the sale of milk in Madison by interstate and intrastate producers who prefer to pasteurize over five miles distant from the city. But both state courts below found that § 7.21 represents a good-faith attempt to safeguard public health by making adequate sanitation *358inspections possible. While we are not bound by these findings, I do not understand the Court to overturn them. Therefore, the fact that § 7.21, like all health regulations, imposes some burden on trade, does not mean that it “discriminates” against interstate commerce.

(3) This health regulation should not be invalidated merely because the Court believes that alternative milk-inspection methods might insure the cleanliness and healthfulness of Dean’s Illinois milk. I find it difficult to explain why the Court uses the “reasonable alternative” concept to protect trade when today it refuses to apply the same principle to protect freedom of speech. Feiner v. New York, 340 U. S. 315. For while the “reasonable alternative” concept has been invoked to protect First Amendment rights, e. g., Schneider v. State, 308 U. S. 147, 162, it has not heretofore been considered an appropriate weapon for striking down local health laws. Since the days of Chief Justice Marshall, federal courts have left states and municipalities free to pass bona fide health regulations subject only “to the paramount authority of Congress if it decides to assume control . . . .” The Minnesota Rate Cases, 230 U. S. 352, 406; Gibbons v. Ogden, 9 Wheat. 1, 203, 204; Mintz v. Baldwin, 289 U. S. 346, 349-350; and see Baldwin v. Seelig, 294 U. S. 511, 524. This established judicial policy of refusing to invalidate genuine local health laws under the Commerce Clause has been approvingly noted even in our recent opinions measuring state regulation by stringent standards. See, e. g., Hood & Sons v. Du Mond, 336 U. S. 525, 531-532. No case is cited, and I have found none, in which a bona fide health law was struck down on the ground that some other method of safeguarding health would be as good as, or better than, the one the Court was called on to review. In my view, to use this ground now elevates the right to traffic in commerce for profit above *359the power of the people to guard the purity of their daily diet of milk.

If, however, the principle announced today is to be followed, the Court should not strike down local health regulations unless satisfied beyond a reasonable doubt that the substitutes it proposes would not lower health standards. I do not think that the Court can so satisfy itself on the basis of its judicial knowledge. And the evidence in the record leads me to the conclusion that the substitute health measures suggested by the Court -do not insure milk as safe as the Madison ordinance requires.

One of the Court’s proposals is that Madison require milk processors to pay reasonable inspection fees at the milk supply “sources.” Experience shows, however, that the fee method gives rise to prolonged litigation over the calculation and collection of the charges. E. g., Sprout v. South Bend, 277 U. S. 163; Capitol Greyhound Lines v. Brice, 339 U. S. 542. To throw local milk regulation into such a quagmire of uncertainty jeopardizes the admirable milk-inspection systems in force in many municipalities. Moreover, nothing in the record before us indicates that the fee system might not be as costly to Dean as having its milk pasteurized in Madison. Surely the Court is not resolving this question by drawing on its “judicial knowledge” to supply information as to comparative costs, convenience, or effectiveness.

The Court’s second proposal is that Madison adopt § 11 of the “Model Milk Ordinance.” The state courts made no findings as to the relative merits of this inspection ordinance and the one chosen by Madison. The evidence indicates to me that enforcement of the Madison law would assure a more healthful quality of milk than that which is entitled to use the label of “Grade A” under the Model Ordinance. Indeed, the United States Board of Public Health, which drafted the Model Ordinance, sug*360gests that the provisions are “minimum” standards only. The Model Ordinance does not provide for continuous investigation of all pasteurization plants as does § 7.21 of the Madison ordinance. Under § 11, moreover, Madison would be required to depend on the Chicago inspection system since Dean’s plants, and the farms supplying them with raw milk, are located in the Chicago milkshed. But there is direct and positive evidence in the record that milk produced under Chicago standards did not meet the Madison requirements.

Furthermore, the Model Ordinance would force the Madison health authorities to rely on “spot checks” by the United States Public Health Service to determine whether Chicago enforced its milk regulations. The evidence shows that these “spot checks” are based on random inspection of farms and pasteurization plants: the United States Public Health Service rates the ten thousand or more dairy farms in the Chicago milkshed by a sampling of no more than two hundred farms. The same sampling technique is employed to inspect pasteurization plants. There was evidence that neither the farms supplying Dean with milk nor Dean’s pasteurization plants were necessarily inspected in the last “spot check” of the Chicago milkshed made two years before the present case was tried.

From what this record shows, and from what it fails to show, I do not think that either of the alternatives suggested by the Court would assure the people of Madison as pure a supply of milk as they receive under their own ordinance. On this record I would uphold the Madison law. At the very least, however, I would not invalidate it without giving the parties a chance to present evidence and get findings on the ultimate issues the Court thinks crucial — namely, the relative merits of the Madison ordinance and the alternatives suggested by the Court today.

Me. Chief Justice Burgee

delivered the opinion of the Court.

In 1973, North Carolina enacted a statute which required, inter alia, all closed containers of apples sold, offered for sale, or shipped into the State to bear “no grade other than the applicable TJ. S. grade or standard.” N. C. Gen. Stat. § 106-189.1 (1973). In an action brought by the Washington State Apple Advertising Commission, a three-judge Federal District Court invalidated the statute insofar as it prohibited the display of Washington State apple grades on the ground that it unconstitutionally discriminated against interstate commerce.

*336The specific questions presented on appeal are (a) whether the Commission had standing to bring this action; (b) if so, whether it satisfied the jurisdictional-amount requirement of 28 U. S. C. § 1331;1 and (c) whether the challenged North Carolina statute constitutes an unconstitutional burden on interstate commerce.

(1)

Washington State is the Nation's largest producer of apples, its crops accounting for approximately 30% of all apples grown domestically and nearly half of all apples shipped in closed containers in interstate commerce. As might be expected, the production and sale of apples on this scale is a multimillion dollar enterprise which plays a significant role in Washington's economy. Because of the importance of the apple industry to the State, its legislature has undertaken to protect and enhance the reputation of Washington apples by establishing a stringent, mandatory inspection program, administered by the State’s Department of Agriculture, which requires all apples shipped in interstate commerce to be tested under strict quality standards and graded accordingly. In all cases, the Washington State grades, which have gained substantial acceptance in the trade, are the equivalent of, or superior to, the comparable grades and standards adopted by the United States Department of Agriculture (USDA). Compliance with the Washington inspection scheme costs the State’s growers approximately $1 million each year.

In addition to the inspection program, the state legislature has sought to enhance the market for Washington apples through the creation of a state agency, the Washington State Apple Advertising Commission, charged with the statutory *337duty of promoting and protecting the State’s apple industry. The Commission itself is composed of 13 Washington apple growers and dealers who are nominated and elected within electoral districts by their fellow growers and dealers. Wash. Rev. Code §§ 15.24.020, 15.24.030 (1974). Among its activities are the promotion of Washington apples in both domestic and foreign markets through advertising, market research and analysis, and public education, as well as scientific research into the uses, development, and improvement of apples. Its activities are financed entirely by assessments levied upon the apple industry, § 15.24.100; in the year during which this litigation began, these assessments totaled approximately $1.75 million. The assessments, while initially fixed by statute, can be increased only upon the majority vote of the apple growers themselves. § 15.24.090.

In 1972, the North Carolina Board of Agriculture adopted an administrative regulation, unique in the 50 States, which in effect required all closed containers of apples shipped into or sold in the State to display either the applicable USDA grade or a notice indicating no classification. State grades were expressly prohibited.2 In addition to its obvious consequence — prohibiting the display of Washington State apple grades on containers of apples shipped into North Carolina, the regulation presented the Washington apple industry with a marketing problem of potentially nationwide significance. Washington apple growers annually ship in commerce approximately 40 million closed containers of apples, nearly 500,000 of which eventually find their way into North Carolina, stamped with the applicable Washington State variety *338and grade. It is the industry’s practice to purchase these containers preprinted with the various apple varieties and grades, prior to harvest. After these containers are filled with apples of the appropriate type and grade, a substantial portion of them are placed in cold-storage warehouses where the grade labels identify the product and facilitate its handling. These apples are then shipped as needed throughout the year; after February 1 of each year, they constitute approximately two-thirds of all apples sold in fresh markets in this country. Since the ultimate destination of these apples is unknown at the time they are placed in storage, compliance with North Carolina’s unique regulation would have required Washington growers to obliterate the printed labels on containers shipped to North Carolina, thus giving their product a damaged appearance. Alternatively, they could have changed their marketing practices to accommodate the needs of the North Carolina market, i. e., repack apples to be shipped to North Carolina in containers bearing only the USD A grade, and/or store the estimated portion of the harvest destined for that market in such special containers. As a last resort, they could discontinue the use of the preprinted containers entirely. None of these costly and less efficient options was very attractive to the industry. Moreover, in the event a number of other States followed North Carolina’s lead, the resultant inability to display the Washington grades could force the Washington growers to abandon the State’s expensive inspection and grading system which their customers had come to know and rely on over the 60-odd years of its existence.

With these problems confronting the industry, the Washington State Apple Advertising Commission petitioned the North Carolina Board of Agriculture to amend its regulation to permit the display of state grades. An administrative hearing was held on the question but no relief was granted. *339Indeed, North Carolina hardened its position shortly thereafter by enacting the regulation into law:

“All apples sold, offered for sale or shipped into this State in closed containers shall bear on the container, bag or other receptacle, no grade other than the applicable U. S. grade or standard or the marking ‘unclassified,’ ‘not graded’ or ‘grade not determined.’ ” N. C. Gen. Stat. § 106-189.1 (1973).

Nonetheless, the Commission once again requested an exemption which would have permitted the Washington apple growers to display both the United States and the Washington State grades on their shipments to North Carolina. This request, too, was denied.

Unsuccessful in its attempts to secure administrative relief, the Commission 3 instituted this action challenging the constitutionality of the statute in the United States District Court for the Eastern District of North Carolina. Its complaint, which invoked the District Court’s jurisdiction under 28 U. S. C. §§ 1331 and 1343, sought a declaration that the statute violated, inter alia, the Commerce Clause of the United States Constitution, Art. I, § 8, cl. 3, insofar as it prohibited the display of Washington State grades, and prayed for a permanent injunction against its enforcement in this manner. A three-judge Federal District Court was convened pursuant to 28 U. S. C. §§ 2281 and 2284 to consider the Commission’s constitutional attack on the statute.

After a hearing, the District Court granted the requested relief. 408 F. Supp. 857 (1976). At the outset, it held that the Commission had standing to challenge the statute both in its own right and on behalf of the Washington State growers and dealers, and that the $10,000 amount-in-controversy *340requirement of § 1331 had been satisfied.4 408 F. Supp., at 858. Proceeding to the merits, the District Court found that the North Carolina statute, while neutral on its face, actually discriminated against Washington State growers and dealers in favor of their local counterparts. Id., at 860-861. This discrimination resulted from the fact that North Carolina, unlike Washington, had never established a grading and inspection system. Hence, the statute had no effect on the existing practices of North Carolina producers; they were still free to use the USDA grade or none at all. Washington growers and dealers, on the other hand, were forced to alter their long-established procedures, at substantial cost, or abandon the North Carolina market. The District Court then concluded that this discrimination against out-of-state competitors was not justified by the asserted local interest — the elimination of deception and confusion from the marketplace — arguably furthered by the statute. Indeed, it noted that the statute was “irrationally” drawn to accomplish that alleged goal since it permitted the marketing of closed containers of apples without any grade at all. Id., at 861-862. The court therefore held that the statute unconstitutionally discriminated against commerce, insofar as it affected the interstate shipment of Washington apples,5 and enjoined its application. This appeal followed and we postponed further consideration of the question of jurisdiction to the hearing of the case on the *341merits sub nom. Holshouser v. Washington State Apple Advertising Comm’n, 429 U. S. 814 (1976).

(2)

In this Court, as before, the North Carolina officials vigorously contest the Washington Commission’s standing to prosecute this action, either in its own right, or on behalf of that State’s apple industry which it purports to represent. At the outset, appellants maintain that the Commission lacks the “personal stake” in the outcome of this litigation essential to its invocation of federal-court jurisdiction. Baker v. Carr, 369 U. S. 186, 204 (1962). The Commission, they point out, is a state agency, not itself engaged in the production and sale of Washington apples or their shipment into North Carolina. Rather, its North Carolina activities are limited to the promotion of Washington apples in that market through advertising.6 Appellants contend that the challenged statute has no impact on that activity since it prohibits only the display of state apple grades on closed containers of apples. Indeed, since the statute imposed no restrictions on the advertisement of Washington apples or grades other than the labeling ban, which affects only those parties actually engaged in the apple trade, the Commission is said to be free to carry on the same activities that it engaged in prior to the regulatory program. Appellants therefore argue that the Commission suffers no injury, economic or otherwise, from the statute’s operation, and, as a result, cannot make out the “case or controversy” between itself and the appellants needed to establish standing in the constitutional sense. E. g., Arlington Heights v. Metropolitan Housing Dev. Corp., 429 U. S. 252, 260-264 (1977); Warth v. Seldin, 422 U. S. 490, 498-499 (1975).

Moreover, appellants assert, the Commission cannot rely on *342the injuries which the statute allegedly inflicts individually or collectively on Washington apple growers and dealers in order to confer standing on itself. Those growers and dealers, appellants argue, are under no disabilities which prevent them from coming forward to protect their own rights if they are, in fact, injured by the statute’s operation. In any event, appellants contend that the Commission is not a proper representative of industry interests. Although this Court has recognized that an association may have standing to assert the claims of its members even where it has suffered no injury from the challenged activity, e. g., Warth v. Seldin, supra, at 511; National Motor Freight Assn. v. United States, 372 U. S. 246 (1963), the Commission is not a traditional voluntary membership organization such as a trade association, for it has no members at all. Thus, since the Commission has no members whose claims it might raise, and since it has suffered no “distinct and palpable injury” to itself, it can assert no more than an abstract concern for the well-being of the Washington apple industry as the basis for its standing. That type of interest, appellants argue, cannot “substitute for the concrete injury required by Art. III.” Simon v. Eastern Ky. Welfare Rights Org., 426 U. S. 26, 40 (1976).

If the Commission were a voluntary membership organization — a typical trade association — its standing to bring this action as the representative of its constituents would be clear under prior decisions of this Court. In Warth v. Seldin, supra, we stated:

“Even in the absence of injury to itself, an association may have standing solely as the representative of its members. . . . The association must allege that its members, or any one of them, are suffering immediate or threatened injury as a result of the challenged action of the sort that would make out a justiciable case had the members themselves brought suit.... So long as this can be established, and so long as the nature of the claim and *343of the relief sought does not make the individual participation of each injured party indispensable to proper resolution of the cause, the association may be an appropriate representative of its members, entitled to invoke the court’s jurisdiction.” 422 U. S., at 511.

See also Simon v. Eastern Ky. Welfare Rights Org., supra, at 39-40; Meek v. Pittenger, 421 U. S. 349, 355-356, n. 5 (1975); Sierra Club v. Morton, 405 U. S. 727, 739 (1972); National Motor Freight Assn. v. United States, supra. We went on in Worth to elaborate on the type of relief that an association could properly pursue on behalf of its members:

“[W]hether an association has standing to invoke the court’s remedial powers on behalf of its members depends in substantial measure on the nature of the relief sought. If in a proper ease the association seeks a declaration, injunction, or some other form of prospective relief, it can reasonably be supposed that the remedy, if granted, will inure to the benefit of those members of the association actually injured. Indeed, in all cases in which we have expressly recognized standing in associations to represent their members, the relief sought has been of this kind.” 422 U. S., at 515.

Thus we have recognized that an association has standing to bring suit on behalf of its members when: (a) its members would otherwise have standing to sue in their own right; (b) the interests it seeks to protect are germane to the organization’s purpose; and (c) neither the claim asserted nor the relief requested requires the participation of individual members in the lawsuit.

The prerequisites to “assoeiational standing” described in Warth are clearly present here. The Commission’s complaint alleged, and the District Court found as a fact, that the North Carolina statute had caused some Washington apple growers and dealers (a) to obliterate Washington State grades from the *344large volume of closed containers destined for the North Carolina market at a cost ranging from 5 to 15 cents per carton; (b) to abandon the use of preprinted containers, thus diminishing the efficiency of their marketing operations; or (c) to lose accounts in North Carolina. Such injuries are direct and sufficient to establish the requisite “case or controversy” between Washington apple producers and appellants. Moreover, the Commission’s attempt to remedy these injuries and to secure the industry’s right to publicize its grading system is central to the Commission’s purpose of protecting and enhancing the market for Washington apples. Finally, neither the interstate commerce claim nor the request for declaratory and injunctive relief requires individualized proof and both are thus properly resolved in a group context.

The only question presented, therefore, is whether, on this record, the Commission’s status as a state agency, rather than a traditional voluntary membership organization, precludes it from asserting the claims of the Washington apple growers and dealers who form its constituency. We think not. The Commission, while admittedly a state agency, for all practical purposes performs the functions of a traditional trade association representing the Washington apple industry. As previously noted, its purpose is the protection and promotion of the Washington apple industry; and, in the pursuit of that end, it has engaged in advertising, market research and analysis, public education campaigns, and scientific research. It thus serves a specialized segment of the State’s economic community which is the primary beneficiary of its activities, including the prosecution of this kind of litigation.

Moreover, while the apple growers and dealers are not “members” of the Commission in the traditional trade association sense, they possess all of the indicia of membership in an organization. They alone elect the members of the Commission; they alone may serve on the Commission; they alone finance its activities, including the costs of this lawsuit, *345through assessments levied upon them. In a very real sense, therefore, the Commission represents the State’s growers and dealers and provides the means by which they express their collective views and protect their collective interests. Nor do we find it significant in determining whether the Commission may properly represent its constituency that "membership” is “compelled” in the form of mandatory assessments. Membership in a union, or its equivalent, is often required. Likewise, membership in a bar association, which may also be an agency of the State, is often a prerequisite to the practice of law. Yet in neither instance would it be reasonable to suggest that such an organization lacked standing to assert the claims of its constituents.

Finally, we note that the interests of the Commission itself may be adversely affected by the outcome of this litigation. The annual assessments paid to the Commission are tied to the volume of apples grown and packaged as “Washington Apples.” In the event the North Carolina statute results in a contraction of the market for Washington apples or prevents any market expansion that might otherwise occur, it could reduce the amount of the assessments due the Commission and used to support its activities. This financial nexus between the interests of the Commission and its constituents coalesces with the other factors noted above to “assure that concrete adverseness which sharpens the presentation of issues upon which the court so largely depends for illumination of difficult constitutional questions.” Baker v. Carr, 369 U. S., at 204; see also NAACP v. Alabama ex rel. Patterson, 357 U. S. 449, 459-460 (1958).

Under the circumstances presented here, it would exalt form over substance to differentiate between the Washington Commission and a traditional trade association representing the individual growers and dealers who collectively form its constituency. We therefore agree with the District Court that the Commission has standing to bring this action in a representational capacity.

*346(3)

We turn next to the appellants' claim that the Commission has failed to satisfy the $10,000 amount-in-controversy requirement of 28 U. S. C. § 1331. As to this, the appellants maintain that the Commission itself has not demonstrated that its right to be free of the restrictions imposed by the challenged statute is worth more than the requisite $10,000. Indeed, they argue that the Commission has made no real effort to do so, but has instead attempted to rely on the actual and threatened injury to the individual Washington apple growers and dealers upon whom the statute has a direct impact. This, they claim, it cannot do, for those growers and dealers are not parties to this litigation. Alternatively, appellants argue that even if the Commission can properly rely on the claims of the individual growers and dealers, it cannot establish the required jurisdictional amount without aggregating those claims. Such aggregation, they argue, is impermissible under this Court’s decisions in Snyder v. Harris, 394 U. S. 332 (1969), and Zahn v. International Paper Co., 414 U.S.291 (1973).

Our determination that the Commission has standing to assert the rights of the individual growers and dealers in a representational capacity disposes of the appellants’ first contention. Obviously, if the Commission has standing to litigate the claims of its constituents, it may also rely on them to meet the requisite amount in controversy. Hence, we proceed to the question of whether those claims were sufficient to confer subject-matter jurisdiction on the District Court. In resolving this issue, we have found it unnecessary to reach the aggregation question posed by the appellants for it does not appear to us “to a legal certainty” that the claims of at least some of the individual growers and dealers will not amount to the required $10,000. St. Paul Mercury Indemnity Co. v. Red Cab Co., 303 U. S. 283, 288-289 (1938).

*347In actions seeking declaratory or injunctive relief, it is well established that the amount in controversy is measured by the value of the object of the litigation. E. g., McNutt v. General Motors Acceptance Corp., 298 U. S. 178, 181 (1936); Glenwood Light & Water Co. v. Mutual Light, Heat & Power Co., 239 U. S. 121, 126 (1915); Hunt v. New York Cotton Exchange, 205 U. S. 322, 336 (1907); 1 J. Moore, Federal Practice ¶¶ 0.95, 0.96 (2d ed. 1975); C. Wright, A Miller, & E. Cooper, Federal Practice & Procedure § 3708 (1976). Here, that object is the right of the individual Washington apple growers and dealers to conduct their business affairs in the North Carolina market free from the interference of the challenged statute. The value of that right is measured by the losses that will follow from the statute’s enforcement. McNutt, supra, at 181; Buck v. Gallagher, 307 U. S. 95, 100 (1939); Kroger Grocery & Baking Co. v. Lutz, 299 U. S. 300, 301 (1936); Packard v. Banton, 264 U. S. 140, 142 (1924).

Here the record demonstrates that the growers and dealers have suffered and will continue to suffer losses of various types. For example, there is evidence supporting the District Court’s finding that individual growers and shippers lost accounts in North Carolina as a direct result of the statute. Obviously, those lost sales could lead to diminished profits. There is also evidence to support the finding that individual growers and dealers incurred substantial costs in complying with the statute. As previously noted, the statute caused some growers and dealers to manually obliterate the Washington grades from closed containers to be shipped to North Carolina at a cost of from 5 to 15 cents per carton. Other dealers decided to alter their marketing practices, not without cost, by repacking apples or abandoning the use of preprinted containers entirely, among other things. Such costs of compliance are properly considered in computing the amount in controversy. Buck v. Gallagher, supra; Packard v. Banton, supra; Allway Taxi, Inc. v. New York, 340 F. Supp. 1120 *348(SDNY), aff’d, 468 F. 2d 624 (CA2 1972). In addition, the statute deprived the growers and dealers of their rights to utilize most effectively the Washington State grades which, the record demonstrates, were of long standing and had gained wide acceptance in the trade. The competitive advantages thus lost could not be regained without incurring additional costs in the form of advertising, etc. Cf. Spock v. David, 502 F. 2d 953, 956 (CA3 1974), rev’d on other grounds, 424 U. S. 828 (1976). Moreover, since many apples eventually shipped to North Carolina will have already gone through the expensive inspection and grading procedure, the challenged statute will have the additional effect of causing growers and dealers to incur inspection costs unnecessarily.

Both the substantial volume of sales in North Carolina— the record demonstrates that in 1974 alone, such sales were in excess of $2 million 7— and the continuing nature of the statute’s interference with the business affairs of the Commission’s constituents, preclude our saying “to a legal certainty,” on this record, that such losses and expenses will not, over time, if they have not done so already, amount to the requisite $10,000 for at least some of the individual growers and dealers. That is sufficient to sustain the District Court’s jurisdiction. The requirements of § 1331 are therefore met.

(4)

We turn finally to the appellants’ claim that the District Court erred in holding that the North Carolina statute violated the Commerce Clause insofar as it prohibited the display of Washington State grades on closed containers of apples shipped into the State. Appellants do not really contest the District Court’s determination that the challenged statute burdened the Washington apple industry by increasing its *349costs of doing business in the North Carolina market and causing it to lose accounts there. Rather, they maintain that any such burdens on the interstate sale of Washington apples were far outweighed by the local benefits flowing from what they contend was a valid exercise of North Carolina’s inherent police powers designed to protect its citizenry from fraud and deception in the marketing of apples.

Prior to the statute’s enactment, appellants point out, apples from 13 different States were shipped into North Carolina for sale. Seven of those States, including the State of Washington, had their own grading systems which, while differing in their standards, used similar descriptive labels (e. g., fancy, extra fancy, etc.). This multiplicity of inconsistent state grades, as the District Court itself found, posed dangers of deception and confusion not only in the North Carolina market, but in the Nation as a whole. The North Carolina statute, appellants claim, was enacted to eliminate this source of deception and confusion by replacing the numerous state grades with a single uniform standard. Moreover, it is contended that North Carolina sought to accomplish this goal of uniformity in an evenhanded manner as evidenced by the fact that its statute applies to all apples sold in closed containers in the State without regard to their point of origin. Nonetheless, appellants argue that the District Court gave “scant attention” to the obvious benefits flowing from the challenged legislation and to the long line of decisions from this Court holding that the States possess “broad powers” to protect local purchasers from fraud and deception in the marketing of foodstuffs. E. g., Florida Lime & Avocado Growers, Inc. v. Paul, 373 U. S. 132 (1963); Pacific States Box & Basket Co. v. White, 296 U. S. 176 (1935); Corn Products Refining Co. v. Eddy, 249 U. S. 427 (1919).

As the appellants properly point out, not every exercise of state authority imposing some burden on the free flow of commerce is invalid. E. g., Great Atlantic & Pacific Tea Co. *350v. Cottrell, 424 U. S. 366, 371 (1976); Freeman v. Hewit, 329 U. S. 249, 252 (1946). Although the Commerce Clause acts as a limitation upon state power even without congressional implementation, e. g., Great Atlantic & Pacific Tea Co., supra, at 370-371; Freeman v. Hewit, supra, at 252; Cooley v. Board of Wardens, 12 How. 299 (1852), our opinions have long recognized that,

“in the absence of conflicting legislation by Congress, there is a residuum of power in the state to make laws governing matters of local concern which nevertheless in some measure affect interstate commerce or even, to some extent, regulate it.” Southern Pacific Co. v. Arizona ex rel. Sullivan, 325 U. S. 761, 767 (1945).

Moreover, as appellants correctly note, that “residuum” is particularly strong when the State acts to protect its citizenry in matters pertaining to the sale of foodstuffs. Florida Lime & Avocado Growers, Inc., supra, at 146. By the same token, however, a finding that state legislation furthers matters of legitimate local concern, even in the health and consumer protection areas, does not end the inquiry. Such a view, we have noted, “would mean that the Commerce Clause of itself imposes no limitations on state action . . . save for the rare instance where a state artlessly discloses an avowed purpose to discriminate against interstate goods.” Dean Milk Co. v. Madison, 340 U. S. 349, 354 (1951). Rather, when such state legislation comes into conflict with the Commerce Clause's overriding requirement of a national “common market,” we are confronted with the task of effecting an accommodation of the competing national and local interests. Pike v. Bruce Church, Inc., 397 U. S. 137, 142 (1970); Great Atlantic & Pacific Tea Co., supra, at 370-372. We turn to that task.

As the District Court correctly found, the challenged statute has the practical effect of not only burdening interstate sales of Washington apples, but also discriminating against them. This discrimination takes various forms. The first, and most *351obvious, is the statute’s consequence of raising the costs of doing business in the North Carolina market for Washington apple growers and dealers, while leaving those of their North Carolina counterparts unaffected. As previously noted, this disparate effect results from the fact that North Carolina apple producers, unlike their Washington competitors, were not forced to alter their marketing practices in order to comply with the statute. They were still free to market their wares under the USDA grade or none at all as they had done prior to the statute’s enactment. Obviously, the increased costs imposed by the statute would tend to shield the local apple industry from the competition of Washington apple growers and dealers who are already at a competitive disadvantage because of their great distance from the North Carolina market.

Second, the statute has the effect of stripping away from the Washington apple industry the competitive and economic advantages it has earned for itself through its expensive inspection and grading system. The record demonstrates that the Washington apple-grading system has gained nationwide acceptance in the apple trade. Indeed, it contains numerous affidavits from apple brokers and dealers located both inside and outside of North Carolina who state their preference, and that of their customers, for apples graded under the Washington, as opposed to the USDA, system because of the former’s greater consistency, its emphasis on color, and its supporting mandatory inspections. Once again, the statute had no similar impact on the North Carolina apple industry and thus operated to its benefit.

Third, by prohibiting Washington growers and dealers from marketing apples under their State’s grades, the statute has a leveling effect which insidiously operates to the advantage of local apple producers. As noted earlier, the Washington State grades are equal or superior to the USDA grades in all corresponding categories. Hence, with free market forces at *352work, Washington sellers would normally enjoy a distinct market advantage vis-a-vis local producers in those categories where the Washington grade is superior. However, because of the statute’s operation, Washington apples which would otherwise qualify for and be sold under the superior Washington grades will now have to be marketed under their inferior USDA counterparts. Such “downgrading” offers the North Carolina apple industry the very sort of protection against competing out-of-state products that the Commerce Clause was designed to prohibit. At worst, it will have the effect of an embargo against those Washington apples in the superior grades as Washington dealers withhold them from the North Carolina market. At best, it will deprive Washington sellers of the market premium that such apples would otherwise command.

Despite the statute’s facial neutrality, the Commission suggests that its discriminatory impact on interstate commerce was not an unintended byproduct and there are some indications in the record to that effect. The most glaring is the response of the North Carolina Agriculture Commissioner to the Commission’s request for an exemption following the statute’s passage in which he indicated that before he could support such an exemption, he would “want to have the sentiment from our apple producers since they were mainly responsible for this legislation being passed . . . .” App. 21 (emphasis added). Moreover, we find it somewhat suspect that North Carolina singled out only closed containers of apples, the very means by which apples are transported in commerce, to effectuate the statute’s ostensible consumer protection purpose when apples are not generally sold at retail in their shipping containers. However, we need not ascribe an economic protection motive to the North Carolina Legislature to resolve this case; we conclude that the challenged statute cannot stand insofar as it prohibits the *353display of Washington State grades even if enacted for the declared purpose of protecting consumers from deception and fraud in the marketplace.

When discrimination against commerce of the type we have found is demonstrated, the burden falls on the State to justify it both in terms of the local benefits flowing from the statute and the unavailability of nondiscriminatory alternatives adequate to preserve the local interests at stake. Dean Milk Co. v. Madison, 340 U. S., at 354. See also Great Atlantic & Pacific Tea Co., 424 U. S., at 373; Pike v. Bruce Church, Inc., 397 U. S., at 142; Polar Ice Cream & Creamery Co. v. Andrews, 375 U. S. 361, 375 n. 9 (1964); Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511, 524 (1935). North Carolina has failed to sustain that burden on both scores.

The several States unquestionably possess a substantial interest in protecting their citizens from confusion and deception in the marketing of foodstuffs, but the challenged statute does remarkably little to further that laudable goal at least with respect to Washington apples and grades. The statute, as already noted, permits the marketing of closed containers of apples under no grades at all. Such a result can hardly be thought to eliminate the problems of deception and confusion created by the multiplicity of differing state grades; indeed, it magnifies them by depriving purchasers of all information concerning the quality of the contents of closed apple containers. Moreover, although the statute is ostensibly a consumer protection measure, it directs its primary efforts, not at the consuming public at large, but at apple wholesalers and brokers who are the principal purchasers of closed containers of apples. And those individuals are presumably the most knowledgeable individuals in this area. Since the statute does nothing at all to purify the flow of information at the retail level, it does little to protect consumers against the problems it was designed to eliminate. Finally, we note that any poten*354tial for confusion and deception created by the Washington grades8 was not of the type that led to the statute’s enactment. Since Washington grades are in all cases equal or superior to their USDA counterparts, they could only “deceive’’ or “confuse” a consumer to his benefit, hardly a harmful result.

In addition, it appears that nondiscriminatory alternatives to the outright ban of Washington State grades are readily available. For example, North Carolina could effectuate its goal by permitting out-of-state growers to utilize state grades only if they also marked their shipments with the applicable USDA label. In that case, the USDA grade would serve as a benchmark against which the consumer could evaluate the quality of the various state grades. If this alternative was for some reason inadequate to eradicate problems caused by state grades inferior to those adopted by the USDA, North Carolina might consider banning those state grades which, unlike Washington’s, could not be demonstrated to be equal or superior to the corresponding USDA categories. Con-cededly, even in this latter instance, some potential for “confusion” might persist. However, it is the type of “confusion" that the national interest in the free flow of goods between the States demands be tolerated.9

The judgment of the District Court is

Affirmed.

Mr. Justice Rehnquist took no part in the consideration or decision of the case.

Mr. Justice Stevens

delivered the opinion of the Court.

A Maryland statute provides that a producer or refiner of petroleum products (1) may not operate any retail service station within the State, and (2) must extend all “voluntary *120allowances” uniformly to all service stations it supplies.1 The questions presented are whether the statute violates either the Commerce or the Due Process Clause of the Constitution of the United States, or is directly or indirectly pre-empted by the congressional expression of policy favoring vigorous competition found in § 2 (b) of the Clayton Act, 38 Stat. 730, as amended by the Robinson-Patman Act, 49 Stat. 1526.2 The Court of Appeals of Maryland answered these questions in *121favor of the validity of the statute. 279 Md. 410, 370 A. 2d 1102 and 372 A. 2d 237 (1977). We affirm.

I

The Maryland statute is an outgrowth of the 1973 shortage of petroleum. In response to complaints about inequitable distribution of gasoline among retail stations, the Governor of Maryland directed the State Comptroller to conduct a market survey. The results of that survey indicated that gasoline stations operated by producers or refiners had received preferential treatment during the period of short supply. The Comptroller therefore proposed legislation which, according to the Court of Appeals, was “designed to correct the inequities in the distribution and pricing of gasoline reflected by the survey.” Id., at 421, 370 A. 2d, at 1109. After legislative hearings and a “special veto hearing” before the Governor, the bill was enacted and signed into law.

Shortly before the effective date of the Act, Exxon Corp. filed a declaratory judgment action challenging the statute in the Circuit Court of Anne Arundel County, Md. The essential facts alleged in the complaint are not in dispute. All of the gasoline sold by Exxon in Maryland is transported into the State from refineries located elsewhere. Although Exxon sells the bulk of this gas to wholesalers and independent retailers, it also sells directly to the consuming public through 36 company-operated stations.3 Exxon uses these stations to test innovative marketing concepts or products.4 Focusing primarily on the Act’s requirement that it discontinue its operation of these 36 retail stations, Exxon’s complaint challenged the *122validity of the statute on both constitutional and federal statutory grounds.5

During the ensuing nine months, six other oil companies instituted comparable actions. Three of these plaintiffs, or their subsidiaries, sell their gasoline in Maryland exclusively through company-operated stations.'6 These refiners, using trade names such as "Red Head” and “Scot,” concentrate largely on high-volume sales with prices consistently lower than those offered by independent dealer-operated major brand stations. Testimony presented by these refiners indicated that company ownership is essential to their method of private brand, low-priced competition. They therefore joined Exxon in its attack on the divestiture provisions of the Maryland statute.

The three other plaintiffs, like Exxon, sell major brands primarily through dealer-operated stations, although they also operate at least one retail station each.7 They, too, challenged the statute’s divestiture provisions, but, in addition, they specially challenged the requirement that “voluntary allowances” be extended uniformly to all retail service stations supplied in the State. Although not defined in the statute, the term “voluntary allowances” refers to temporary price reductions granted by the oil companies to independent dealers who *123are injured by local competitive price reductions of competing retailers.8 The oil companies regard these temporary allowances as legitimate price reductions protected by § 2 (b). In advance of trial, Exxon, Shell, and Gulf moved for a partial summary judgment declaring this portion of the Act invalid as in conflict with § 2 (b).

The Circuit Court granted the motion, and the trial then focused on the validity of the divestiture provisions. As brought out during the trial, the salient characteristics of the Maryland retail gasoline market are as follows: Approximately 3,800 retail service stations in Maryland sell over 20 different brands of gasoline. However, no petroleum products are produced or refined in Maryland, and the number of stations actually operated by a refiner or an affiliate is relatively small, representing about 5% of the total number of Maryland retailers.

The refiners introduced evidence indicating that their ownership of retail service stations has produced significant benefits for the consuming public.9 Moreover, the three refiners that now market solely through company-operated stations may elect to withdraw from the Maryland market altogether if the statute is enforced. There was, however, no evidence that the total quantity of petroleum products shipped into Maryland would be affected by the statute.10 After trial, the Circuit Court held the entire statute invalid, primarily on substantive due process grounds.

The Maryland Court of Appeals reversed, rejecting all of the refiners’ attacks against both the divestiture provisions and *124the voluntary-allowance provision. Most of those attacks are not pursued here;11 instead, appellants have focused their appeals on the claims that the Maryland statute violates the Due Process and Commerce Clauses and that it is in conflict with the Robinson-Patman Act.

II

Appellants’ substantive due process argument requires little discussion.12 The evidence presented by the refiners may cast sorpe doubt on the wisdom of the statute, but it is, by now, absolutely clear that the Due Process Clause does not empower the. judiciary “to sit as a 'superlegislature to weigh the wisdom of legislation’ . . . .” Ferguson v. Skrupa, 372 U. S. 726, 731 (citation omitted). Responding to evidence that producers and refiners were favoring company-operated stations in the allocation of gasoline and that this would eventually decrease the competitiveness of the retail market, the State enacted a law prohibiting producers and refiners from operating their own stations. Appellants argue that this response is irrational and that it will frustrate rather than further the State’s desired goal of enhancing competition. But, as the Court of Appeals observed, this argument rests simply on an evaluation of the economic wisdom of the statute, 279 Md., at 428, 370 A. 2d, at 1112, and cannot override the State’s authority “to legislate against what are found to be injurious practices in their internal commercial and business affairs ....” Lincoln Federal Labor Union v. Northwestern Iron & Metal Co., 335 U. S. 525, 536.13 Regardless of the ultimate economic *125efficacy of the statute, we have no hesitancy in concluding that it bears a reasonable relation to the State’s legitimate purpose in controlling the gasoline retail market, and we therefore reject appellants’ due process claim.

Ill

Appellants argue that the divestiture provisions of the Maryland statute violate the Commerce Clause in three ways: (1) by discriminating against interstate commerce; (2) by unduly burdening interstate commerce; and (3) by imposing controls on a commercial activity of such an essentially interstate character that it is not amenable to state regulation.

Plainly, the Maryland statute does not discriminate against interstate goods, nor does it favor local producers and refiners. Since Maryland’s entire gasoline supply flows in interstate commerce and since there are no local producers or refiners, such claims of disparate treatment' between interstate and local commerce would be meritless. Appellants, however, focus on the retail market, arguing that the effect of the statute is to protect in-state independent dealers from out-of-state competition. They contend that the divestiture provisions “create a protected enclave for Maryland independent dealers ... .” 14 As support for this proposition, they rely on the fact that the burden of the divestiture requirements falls solely on interstate companies. But this fact does not lead, either logically or as a practical matter, to a conclusion that the State is discriminating against interstate commerce at the retail level.

As the record shows, there are several major interstate marketers of petroleum that own and operate their own retail *126gasoline stations.15 These interstate dealers, who compete directly with the Maryland independent dealers, are not affected by the Act because they do not refine or produce gasoline. In fact, the Act creates no barriers whatsoever against interstate independent dealers; it does not prohibit the flow of interstate goods, place added costs upon them, or distinguish between in-state and out-of-state companies in the retail market. The absence of any of these factors fully distinguishes this case from those in which a State has been found to have discriminated against interstate commerce. See, e. g., Hunt v. Washington Apple Advertising Comm’n, 432 U. S. 333; Dean Milk Co. v. Madison, 340 U. S. 349. For instance, the Court in Hunt noted that the challenged state statute raised the cost of doing business for out-of-state dealers, and, in various other ways, favored the in-state dealer in the local market. 432 U. S., at 351-352. No comparable claim can be made here. While the refiners will no longer enjoy their same status in the Maryland market, in-state independent dealers will have no competitive advantage over out-of-state dealers. The fact that the burden of a state regulation falls on some interstate companies does not, by itself, establish a claim of discrimination against interstate commerce.16

*127Appellants argue, however, that this fact does show that the Maryland statute impermissibly burdens interstate commerce. They point to evidence in the record which indicates that, because of the divestiture requirements, at least three refiners will stop selling in Maryland, and which also supports their claim that the elimination of company-operated stations will deprive the consumer of certain special services. Even if we assume the truth of both assertions, neither warrants a finding that the statute impermissibly burdens interstate commerce.

Some refiners may choose to withdraw entirely from the Maryland market, but there is no reason to assume that their share of the entire supply will not be promptly replaced by other interstate refiners. The source of the consumers’ supply may switch from company-operated stations to independent dealers, but interstate commerce is not subjected to an impermissible burden simply because an otherwise valid regulation causes some business to shift from one interstate supplier to another.

The crux of appellants’ claim is that, regardless of whether the State has interfered with the movement of goods in interstate commerce, it has interfered “with the natural functioning of the interstate market either through prohibition or through burdensome regulation.” Hughes v. Alexandria Scrap Corp., 426 U. S. 794, 806. Appellants then claim that the statute “will surely change the market structure by weakening the independent refiners . ...”17 We cannot, however, accept appellants’ underlying notion that the Commerce Clause protects the particular structure or methods of operation in a retail market. See Breard v. Alexandria, 341 U. S. 622. As indicated by the Court in Hughes, the Clause protects the interstate market, not particular interstate firms, from prohib*128itive or burdensome regulations. It may be true that the consuming public will be injured by the loss of the high-volume, low-priced stations operated by the independent refiners, but again that argument relates to the wisdom of the statute, not to its burden on commerce.

Finally, we cannot adopt appellants' novel suggestion that because the economic market for petroleum products is nationwide, no State has the power to regulate the retail marketing of gas. Appellants point out that many state legislatures have either enacted or considered proposals similar to Maryland's,18 and that the cumulative effect of this sort of legislation may have serious implications for their national marketing operations. While this concern is a significant one, we do not find that the Commerce Clause, by its own force, pre-empts the field of retail gas marketing. To be sure, “the Commerce Clause acts as a limitation upon state power even without congressional implementation.'' Hunt v. Washington Apple Advertising Comm’n, supra, at 350. But this Court has only rarely held that the Commerce Clause itself pre-empts an entire field from state regulation, and then only when a lack of national uniformity would impede the flow of interstate goods. See Wabash, St. L. & P. R. Co. v. Illinois, 118 U. S. 557; see also Cooley v. Board of Wardens, 12 How. 299, 319. The evil that appellants perceive in this litigation is not that the several States will enact differing regulations, but rather that they will all conclude that divestiture provisions are warranted. The problem thus is not one of national uniformity. In the absence of a relevant congressional declaration of policy, or a showing of a specific discrimination against, or burdening *129of, interstate commerce, we cannot conclude that the States are without power to regulate in this area.

IV

Exxon, Phillips, Shell, and Gulf contend that the requirement that voluntary allowances be extended to all retail service stations is either in direct conflict with § 2 (b) of the Clayton Act, as amended by the Robinson-Patman Act, or, more generally, in conflict with the basic federal policy in favor of competition, which is reflected in the Sherman Act as well as § 2 (b). In rejecting these contentions, the Maryland Court of Appeals noted that the Maryland statute covered two different competitive situations.19 In the first situation a competing retailer lowers its price on its own, and the oil company gives its own retailer a price reduction to enable it to meet that lower price. In the second situation, the competing retailer’s lower price is subsidized by its supplier, and the oil company gives its own retailer a price reduction to meet the competition. The good-faith defense of § 2 (b) is clearly not available to the oil company in the first situation because the voluntary allowance would not be a response to competition from another oil company. See FTC v. Sun Oil Co., 371 U .S. 505. In the second situation the law is unsettled,20 but the *130Court of Appeals concluded that the defense would also be unavailable. The court therefore reasoned that there was no conflict between the Maryland statute and § 2 (b), since the statute did not apply to any allowance protected by federal law. In our opinion, it is not necessary to decide whether the § 2 (b) defense would apply in the second situation, for even assuming that it does, there is no conflict between the Maryland statute and the Robinson-Patman Act sufficient to require pre-emption.

Appellants’ first argument is that compliance with the Maryland statute may cause them to violate the Robinson-Patman Act. They stress the possibility that the requirement that a price reduction be made on a statewide basis may result in discrimination between customers who would otherwise receive the same price, and they describe various hypothetical situations to illustrate this point.21 But, “[i]n this as in other areas of coincident federal and state regulation, the 'teaching of this Court’s decisions . . . enjoin[s] seeking out conflicts between state and federal regulation where none clearly exists.’ Huron Cement Co. v. Detroit, 362 U. S. 440, 446.” Seagram & Sons, Inc. v. Hostetter, 384 U. S. 35, 45. See also State v. Texaco, Inc., 14 Wis. 2d 625, 111 N. W. 2d 918 (1961). The Court in Seagram & Sons went on to say that "[a]lthough it is possible to envision circumstances under which price dis-*131criminations proscribed by the Robinson-Patman Act might be compelled by [the state statute], the existence of such potential conflicts is entirely too speculative in the present posture of this case” to warrant pre-emption. 384 U. S., at 46. That counsel of restraint applies with even greater force here. For even if we were to delve into the hypothetical situations posed by appellants, we would not be presented with a state statute that requires a violation of the Robinson-Patman Act. Instead, the alleged “conflict” here is in the possibility that the Maryland statute may require uniformity in some situations in which the Robinson-Patman Act would permit localized discrimination.22 This sort of hypothetical conflict is not sufficient to warrant pre-emption.

Appellants, however, also claim that the Robinson-Patman Act does not simply permit localized discrimination, but actually establishes a federal right to engage in discriminatory pricing in certain situations. They argue that this federal right may be found directly in § 2 (b), or, more generally, in our Nation's basic policy favoring competition as reflected in the Sherman Act as well as § 2 (b). We find neither argument persuasive.

The proviso in § 2 (b) of the Clayton Act, as amended by *132the Robinson-Patman Act, is merely an exception to that statute’s broad prohibition against discriminatory pricing. It created no new federal right; quite the contrary, it defined a specific, limited defense, and even narrowed the good-faith defense that had previously existed.23 To be sure, the defense is an important one, and the interpretation of its contours has been informed by the underlying national policy favoring competition which it reflects.24 But it is illogical to infer that by excluding certain competitive behavior from the general ban against discriminatory pricing, Congress intended to preempt the States’ power to prohibit any conduct within that exclusion. This Court is generally reluctant to infer preemption, see, e. g., De Canas v. Bica, 424 U. S. 351, 357-358, n. 5; Merrill Lynch, Pierce, Fenner & Smith v. Ware, 414 U. S. 117, 127, and it would be particularly inappropriate to do so in this case because the basic purposes of the state statute and the Robinson-Patman Act are similar. Both reflect a policy choice favoring the interest in equal treatment of all customers *133over the interest in allowing sellers freedom to make selective competitive decisions.25

Appellants point out that the Robinson-Patman Act itself may be characterized as an exception to, or a qualification of, the more basic national policy favoring free competition,26 and argue that the Maryland statute “undermin[es]” the competitive balance that Congress struck between the Robinson-Patman and Sherman Acts.27 This is merely another way of stating that the Maryland statute will have an anticompetitive effect. In this sense, there is a conflict between the statute and the central policy of the Sherman Act — our “charter of economic liberty.” Northern Pacific R. Co. v. United States, 356 U. S. 1, 4. Nevertheless, this sort of conflict cannot itself constitute a sufficient reason for invalidating the Maryland statute. For if an adverse effect on competition were, in and of itself, enough to render a state statute invalid, the States’ power to engage in economic regulation would be effectively destroyed.28 We are, therefore, satisfied that neither the broad implications of the Sherman Act nor the Robinson-Patman Act can fairly *134be construed as a congressional decision to pre-empt the power of the Maryland Legislature to enact this law.

The judgment is affirmed.

So ordered.

Mr. Justice Powell took no part in the consideration or decision of these cases.

Mr. Justice Blackmun,

concurring in part and dissenting in part.

Although I agree that the Maryland Motor Fuel Inspection Law1 does not offend substantive due process or federal anti*135trust policy, I dissent from Part III of the Court’s opinion because it fails to condemn impermissible discrimination against interstate commerce in retail gasoline marketing. The divestiture provisions, Md. Code Ann., Art. 56, §§ 157E (b) and (c) (Supp. 1977) (hereinafter referred to as §§ (b) and (c)), preclude out-of-state competitors from retailing gasoline within Maryland. The effect is to protect in-state retail service station dealers from the competition of the out-of-state businesses. This protectionist discrimination is not justified by any legitimate state interest that cannot be vindicated by more evenhanded regulation. Sections (b) and (c), therefore, violate the Commerce Clause.2

I

In Maryland the retail marketing of gasoline is interstate commerce, for all petroleum products come from outside the State. Retailers serve interstate travelers. To the extent that particular retailers succeed or fail in their businesses, the interstate wholesale market for petroleum products is affected. Cf. Dean Milk Co. v. Madison, 340 U. S. 349 (1951).3 The *136regulation of retail gasoline sales is therefore within the scope of the Commerce Clause. See ibid.; Minnesota v. Barber, 136 U. S. 313 (1890).4

A

The Commerce Clause forbids discrimination against interstate commerce, which repeatedly has been held to mean that States and localities may not discriminate against the transactions of out-of-state actors in interstate markets. E. g., Hunt v. Washington Apple Advertising Comm’n, 432 U. S. 333, 350-352 (1977); Halliburton Oil Well Co. v. Reily, 373 U. S. 64, 69-73 (1963); Dean Milk Co. v. Madison, 340 U. S., at 354; Best & Co. v. Maxwell, 311 U. S. 454, 455-456 (1940). The discrimination need not appear on the face of the state or local regulation. “The commerce clause forbids discrimination, whether forthright or ingenious. In each case it is our duty to determine whether the statute under attack, whatever its name may be, will in its practical operation work discrimination against interstate commerce.” Ibid, (footnote omitted). The state or local authority need not intend to discriminate in order to offend the policy of maintaining a free-flowing national economy. As demonstrated in Hunt, a statute that on its face restricts both intrastate and interstate transactions may violate the Clause by having the “practical effect” of discriminating in its operation. 432 U. S., at 350-352.

If discrimination results from a statute, the burden falls upon the state or local government to demonstrate legitimate local benefits justifying the inequality and to show that less discriminatory alternatives cannot protect the local interests. *137 Id., at 353; Dean Milk Co. v. Madison, 340 U. S., at 354. This Court does not merely accept without analysis purported local interests. Instead, it independently identifies the character of the interests and judges for itself whether alternatives will be adequate. For example, in Dean Milk the city attempted to justify a milk pasteurization ordinance by claiming it to be a necessary health measure. The city’s assertion was not conclusive, however:

“A different view, that the ordinance is valid simply because it professes to be a health measure, would mean that the Commerce Clause of itself imposes no limitations on state action other than those laid down by the Due Process Clause, save for the rare instance where a state artlessly discloses an avowed purpose to discriminate against interstate goods.” Ibid.

In an independent assessment of the asserted purpose, the Court determined exactly how the ordinance protected public health and then concluded that other measures could accomplish the same ends. Id., at 354-356. The city’s public health purpose therefore did not justify the discrimination, and the ordinance violated the Commerce Clause.

B

With this background, the unconstitutional discrimination in the Maryland statute becomes apparent. No facial inequality exists; §§ (b) and (c) preclude all refiners and producers from marketing gasoline at the retail level. But given the structure of the retail gasoline market in Maryland, the effect of §§ (b) and (c) is to exclude a class of predominantly out-of-state gasoline retailers while providing protection from competition to a class of nonintegrated retailers that is overwhelmingly composed of local businessmen. In 1974, of the 3,780 gasoline service stations in the State, 3,547 were operated by nonintegrated local retail dealers. App. 191, 569, 755. Of the 233 company-operated stations, 197 belonged to out-of-*138state integrated producers or refiners. Id., at 190-191. Thirty-four were operated by nonintegrated companies that would not have been affected immediately by the Maryland statute.5 Ibid. The only in-state integrated petroleum firm, Crown Central Petroleum, Inc., operated just two service stations. Id., at 189. Of the class of stations statutorily insulated from the competition of the out-of-state integrated firms, then, more than 99% were operated by local business interests. Of the class of enterprises excluded entirely from participation in the retail gasoline market, 95% were out-of-state firms, operating 98% of the stations in the class. Ibid.

The discrimination suffered by the out-of-state integrated producers and refiners is significant. Five of the excluded enterprises, Ashland Oil, Inc., BP Oil, Inc., Kayo Oil Co., Petroleum Marketing Corp., and Southern States Cooperative, Inc., market nonbranded gasoline through price competition rather than through brand recognition. Of the 98 stations marketing gasoline in this manner, all but 6 are company operated. The company operations result from the dominant fact of price competition marketing. According to repeated testimony from petroleum economics experts and officers of price marketers — testimony that the trial court did not discredit — such nonbranded stations can compete successfully only if they have day-to-day control of the retail price of their products, the hours of operation of their stations, and related business details. App. 320, 357, 370-371, 449-451, 503-504, *139517, 529-530; Joint App. to Jurisdictional Statements 102a et seq. Only with such control can sufficient sales volume be achieved to produce satisfactory profits at prices two to three cents a gallon below those of the major branded stations. Dealer operation of stations precludes such control because of the illegality of vertical price fixing. See, e. g., 15 U. S. C. § 1 (1976 ed.); White Motor Co. v. United States, 372 U. S. 253 (1963). Therefore, because §§ (b) and (c) forbid company operations, these out-of-state competitors will have to abandon the Maryland retail market altogether. App. 100, 357-358, 455, 519; Joint App. to Jurisdictional Statements 103a et seq. 6 For the same reason 32 other out-of-state national nonbranded integrated marketers, who operate their own stations without dealers, will be precluded from entering the Maryland retail gasoline market.

The record also contains testimony that the discrimination will burden the operations of major branded companies, such as appellants Exxon, Phillips, Shell, and Gulf, all of which are out-of-state firms. Most importantly, §§ (b) and (c) will preclude these companies, as well as those mentioned in the previous paragraph, from competing directly for the profits of retail marketing. According to Richard T. Harvin, retail sales manager for Exxon’s eastern marketing region, Exxon’s company-operated stations in Maryland annually return 15% of the company’s investment — a profit of $700,000 in 1974. App. 316. Sections (b) and (c) will force this return to be shared with the local dealers. In addition, the ban of the sections will preclude the majors from enhancing brand recognition and consumer acceptance through retail outlets with company-controlled standards. Id., at 316, 320, 647, 668-669. Their ability directly to monitor consumer preferences and *140reactions will be diminished. Id., at 315, 649, 669. And their opportunity for experimentation with retail marketing techniques will be curtailed. Id., at 316-317, 647-649, 669. In short, the divestiture provisions, which will require the appellant majors to cease operation of property valued at more than $10 million, will inflict significant economic hardship on Maryland’s major brand companies, all of which are out-of-state firms.

Similar hardship is not imposed upon the local service station dealers by the divestiture provisions. Indeed, rather than restricting their ability to compete, the Maryland Act effectively and perhaps intentionally improves their competitive position by insulating them from competition by out-of-state integrated producers and refiners. In its answers to the various complaints in this case, the State repeatedly conceded that the Act was intended to protect “the retail dealer as an independent businessman [by] reducing the control and dominance of the vertically integrated petroleum producer and refiner in the retail market.” Id., at 33; see id., at 51, 54, 104, 128, 132, 145, 147. At trial the State’s expert said that the legislation would have the effect of protecting the local dealers against the out-of-state competition. Id., at 613. In short, the foundation of the discrimination in this case is that the local dealers may continue to enter retail transactions and to compete for retail profits while the statute will deny similar opportunities to the class composed almost entirely of out-of-state businesses.7

*141With discrimination proved against interstate commerce, the burden falls upon the State to justify the distinction with legitimate state interests that cannot be vindicated with more evenhanded regulation. On the record before the Court, the State fails to carry its burden. It asserts only in general terms a desire to maintain competition in gasoline retailing. Although this is a laudable goal, it cannot be accepted without further analysis, just as the Court could not accept the mere assertion of a public health justification in Dean Milk. Here, the State ignores the second half of its responsibility; it does not even attempt to demonstrate why competition cannot be preserved without banning the out-of-state interests from the retail market.

The State’s showing may be so meager because any legitimate interest in competition can be vindicated with more evenhanded regulation. First, to the extent that the State’s interest in competition is nothing more than a desire to protect particular competitors — less efficient local businessmen — from the legal competition of more efficient out-of-state firms, the interest is illegitimate under the Commerce Clause. A national economy would hardly flourish if each State could effectively insist that local nonintegrated dealers handle product retailing to the exclusion of out-of-state integrated firms that would not have sufficient local political clout to challenge the influence of local businessmen with their local government leaders.8 Each State would be encouraged to “legislate accord*142ing to its estimate of its own interests, the importance of its own products, and the local advantages or disadvantages of its position in a political or commercial view.” J. Story, Commentaries on the Constitution of the United States § 259 (4th ed. 1873), quoted in H. P. Hood Sons v. Du Mond, 336 U. S. 525, 533 (1949). See also, e. g., The Federalist, Nos. 7, 11, 12 (Hamilton), No. 42 (Madison). The Commerce Clause simply does not countenance such parochialism.

Second, a legitimate concern of the State could be to limit the economic power of vertical integration. But nothing in the record suggests that the vertical integration that has *143already occurred in the Maryland petroleum market has inhibited competition. Indeed, the trial court found that the retail market, dominated by 3,547 dealer outlets constituting more than 90% of the State’s service stations, is highly competitive.9 Therefore, the State has shown no need for the divestiture of existing company-owned stations required by § (c). The legitimacy of any concern about future integration, which could support the discrimination of § (b), is suspect because of the exemption granted wholesalers, which, not surprisingly, are local businesses able to influence the state legislature.10 See n. 7, supra.

*144Third, the State appears to be concerned about unfair competitive behavior such as predatory pricing or inequitable allocation of petroleum products by the integrated firms. These are the only examples of specific misconduct asserted in the State’s answers. App. 33-34, 54-55, 81-83, 109-111, 133-134, 148-149. But none of the concerns support the discrimination in §§ (b) and (c). There is no proof in the record that any significant portion of the class of out-of-state firms burdened by the divestiture sections has engaged in such misconduct. Furthermore, predatory pricing and unfair allocation already have been prohibited by both state and federal law. See, e. g., Emergency Petroleum Allocation Act of 1973, 87 Stat. 628, 15 U. S. C. §751 et seq. (1976 ed.); Energy Policy and Conservation Act, § 461, 89 Stat. 955, 15 U. S. C. § 760g (1976 ed.); Maryland Motor Fuel Inspection Law, Md. Code Ann., Art. 56, § 157E (f) (Supp. 1977); Maryland Antitrust Act, Md. Com. Law Code Ann. § 11-201 et seq. (1975); Maryland Unfair Sales Act, Md. Com. Law Code Ann. § 11-401 et seq. (1975). Less discriminatory legislation, which would regulate the leasing of all service stations, not just those owned by the out-of-state integrated producers and refiners, could prevent whatever evils arise from short-*145term leases. Cf. Maryland Gasoline Products Marketing Act, Md. Com. Law Code Ann. § 11-304 (g) (Supp, 1977).11

In sum, the State has asserted before this Court only a vague interest in preserving competition in its retail gasoline market. It has not shown why its interest cannot be vindicated by legislation less discriminatory toward out-of-state retailers. It therefore has not met its burden to justify the discrimination inherent in §§ (b) and (c), and they violate the Commerce Clause.

II

The arguments of the Court’s opinion, the Maryland Court of Appeals decision,12 and appellees do not remove the unconstitutional taint from the discrimination inherent in §§ (b) and (c).

A

The Court offers essentially three responses to the discrimination in the retail gasoline market imposed by the divestiture provisions.13 First, the Court says that the discrimination *146against the class of out-of-state producers and refiners does not violate the Commerce Clause because the State has not imposed similar discrimination against other out-of-state retailers. Ante, at 125-126. This is said to distinguish the present case from Hunt v. Washington Apple Advertising Comm’n. In fact, however, the unconstitutional discrimination in Hunt was not against all out-of-state interests. North Carolina had enacted a statute requiring that apples marketed in closed containers within the State bear “ ‘no grade other than the applicable U. S. grade or standard.’ ” 432 U. S., at 335. The Commission contended that the provision discriminated against interstate commerce because it prohibited the display of superior Washington State apple grading marks. The Court did not strike down the provision because it discriminated against the marketing techniques of all out-of-state growers. The provision imposed no discrimination on growers from States that employed only the United States Department of Agriculture grading system.14 Despite this *147lack of universal discrimination, the Court declared the provision unconstitutional because it discriminated against a single segment of out-of-state marketers of apples, namely, the Washington State growers who employed the superior grading system. In this regard, the Maryland divestiture provisions are identical to, not distinguishable from, the North Carolina statute in Hunt. Here, the discrimination has been imposed against a segment of the out-of-state retailers of gasoline, namely, those who also refine or produce petroleum.

To accept the argument of the Court, that is, that discrimination must be universal to offend the Commerce Clause, naively will foster protectionist discrimination against interstate commerce. In the future, States will be able to insulate in-state interests from competition by identifying the most potent segments of out-of-state business, banning them, and permitting less effective out-of-state actors to remain. The record shows that the Court permits Maryland to effect just such discrimination in this case. The State bans the most powerful out-of-state firms from retailing gasoline within its boundaries. It then insulates the forced divestiture of 199 service stations from constitutional attack by permitting out-of-state firms such as Pantry Pride, Pisca, Hi-Way, and Midway to continue to operate 34 gasoline stations. Effective out-of-state competition is thereby emasculated — no doubt, an ingenious discrimination. But as stated at the outset, “the commerce clause forbids discrimination, whether forthright or ingenious.” Best & Co. v. Maxwell, 311 U. S., at 455.

Second, the Court contends, as a subpart of its primary argument, that the discrimination in Hunt “raised the cost of doing business for out-of-state dealers, and, in various other ways, favored the in-state dealer in the local market. 432 U. S., at 351-352. No comparable claim can be made here.” Ante, at 126. Once it is seen that the discrimination in Hunt raised the cost of doing business for only one group of the out-of-state marketers of apples, the fallacy of the Court’s *148argument appears. In fact, here the burden imposed upon the class of out-of-state retailers subject to the discrimination of §§ (b) and (c) far exceeds the burdens in Hunt. In Hunt the statute merely increased costs and deprived the Washington growers of the competitive advantages of the use of then-grading system. Here, the statute bans the refiners and producers from the retail market altogether — a burden that lacks comparability with the effects in Hunt only because it is more severe.

Third, the Court asserts without citation: "The fact that the burden of a state regulation falls on some interstate companies does not, by itself, establish a claim of discrimination against interstate commerce.” Ante, at 126. This proposition is correct only to the extent that it is incomplete; it does not apply to the facts present here. It is true that merely demonstrating a burden on some out-of-state actors does not prove unconstitutional discrimination. But when the burden is significant, when it falls on the most numerous and effective group of out-of-state competitors, when a similar burden does not fall on the class of protected in-state businessmen, and when the State cannot justify the'resulting disparity by showing that its legislative interests cannot be vindicated by more evenhanded regulation, unconstitutional discrimination exists. The facts of this litigation demonstrate such discrimination, and the Court does not argue persuasively to the contrary.

B

The contentions of the Maryland Court of Appeals, which also found no violation of the Commerce Clause, are no more convincing than the arguments of the Court’s opinion. First, the Court of Appeals reasoned that §§ (b) and (c) did not discriminate against the class of out-of-state refiners and producers because the wholesale flow of petroleum products into the State was not restricted. 279 Md. 410, 431, 370 A. 2d 1102, 1114 (1977). This supposedly distinguished the present *149facts from those of Dean Milk Co. v. Madison, which involved unconstitutional discrimination against interstate commerce. To begin with, however, the distinction drawn by the Court of Appeals is basically irrelevant. The Maryland statute has not effected discrimination with regard to the wholesaling or interstate transport of petroleum. The discrimination exists with regard to retailing. The fact that gasoline will continue to flow into the State does not permit the State to deny out-of-state firms the opportunity to retail it once it arrives.

Furthermore, Dean Milk cannot be distinguished on the ground asserted by the Court of Appeals. There, this Court invalidated § 7.21 of the General Ordinances of the city of Madison (1949), which outlawed the local sale of milk not pasteurized within five miles of the city. The section did not legally or effectively block the flow of out-of-state milk into Madison to any greater extent than the restrictions on sales of gasoline by out-of-state companies block the flow of gasoline here. In Dean Milk out-of-state producers could bring their milk to Madison, have it pasteurized in Madison, and sell it in Madison without violating § 7.21. If the flow of milk were at all restricted, it was merely because the out-of-state producers chose not to deal with the Madison pasteurizers. Similarly, the flow of gasoline into Maryland may be restricted if the out-of-state producers and refiners choose not to supply the dealers who replace the company-owned operations.15

Second, the Court of Appeals said the Maryland legislation did not offend the Commerce Clause because the legislature intended to preserve competition, not to discriminate against interstate commerce. 279 Md., at 431, 370 A. 2d, at 1114. *150With this argument, the court fell into the same trap that confines the State’s proffered justifications for the discrimination of §§ (b) and (c). To begin with, the fact that no discrimination was intended is irrelevant where, as here, discriminatory effects result from the statutory scheme. Furthermore, the fact that the legislature might have had a laudable intent when it passed the law cannot by itself justify the divestiture provisions. The State must also show that its interests cannot be vindicated by less discriminatory alternatives. The Court of Appeals erroneously failed to require such a showing from the appellees.

Third, the Court of Appeals resurrected the outdated notion that retailing is merely local activity not subject to the strictures of the Commerce Clause. 279 Md., at 432, 370 A. 2d, at 1114-1115, citing Crescent Oil Co. v. Mississippi, 257 U. S. 129 (1921). In Crescent Oil the Court said that the operation of cotton gins was local manufacturing rather than interstate commerce. As explained at the beginning of Part I of this opinion, however, the interstate character of the retail gasoline market and 57 years of intervening constitutional and economic development prevent the application of Crescent Oil to the facts of this litigation. See nn. 3 and 4, and accompanying text, supra.

C

Finally, nothing in the argument of the appellees saves the distinctions in §§ (b) and (c) from the taint of unconstitutionality. First, the State argues that discrimination against interstate commerce has not occurred because “[n]o nexus between interstate as opposed to local interests inheres in the production or refining of petroleum.” Brief for Appellees 23. Although this statement might be correct in the abstract, it is incorrect in reality, given the structure of the Maryland petroleum market. Due to geological formation as so far known, no petroleum is produced in Maryland; due to the economics of production and refining, as well as to the geology, *151no petroleum is refined in Maryland. As a matter of actual fact, then, an inherent nexus does exist between the out-of-state status of producers and refiners and the distribution and retailing of gasoline in Maryland. The Commerce Clause does not forbid only legislation that discriminates under all factual circumstances. It forbids discrimination in effect against interstate commerce on the specific facts of each case. If production or refining of gasoline occurred in Maryland, §§ (b) and (c) might not be unconstitutional. Under those different circumstances, however, the producers and refiners would have a fair opportunity to influence their local legislators and thereby to prevent the enactment of economically disruptive legislation. Under those circumstances, the economic disruption would be felt directly in Maryland, which would tend to malee the local political processes responsive to the problems thereby created. Under those circumstances, §§ (b) and (c) might never have been passed. In this case, however, the economic disruption of the sections is visited upon out-of-state economic interests and not upon in-state businesses. One of the basic assumptions of the Commerce Clause is that local political systems will tend to be unresponsive to problems not felt by local constituents; instead, local political units are expected to act in their constituents’ interests.16 One of the basic purposes of the Clause, therefore, is to prevent the vindication of such self-interest from unfairly burdening out-of-state concerns and thereby disrupting the national economy.

*152Second, appellees argue, as did the Court of Appeals, that §§ (b) and (c) do not discriminate impermissibly because the Maryland Legislature passed them with the intent to preserve competition. As explained above, however, the mere assertion of a laudable purpose does not carry the State’s burden to justify the discriminatory effects of the statute. See Parts I-B and II-B, supra.

Third, appellees rely upon the Court of Appeals’ contention that unconstitutional discrimination against interstate commerce can be found only where the flow of interstate goods is curtailed. Appellees’ assertion fares no better than did the court’s because the appellees fail to show how the effect on the flow of interstate goods varies in kind between this case and Dean Milk. See Part II-B, supra.

Ill

The Court’s decision brings to mind the well-known words of Mr. Justice Cardozo:

“To give entrance to [protectionism] would be to invite a speedy end of our national solidarity. The Constitution was framed under the dominion of a political philosophy less parochial in range. It was framed upon the theory that the peoples of the several states must sink or swim together, and that in the long run prosperity and salvation are in union and not division.” Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511, 523 (1935).

Today, the Court fails to heed the Justice’s admonition. The parochial political philosophy of the Maryland Legislature thereby prevails. I would reverse the judgment of the Maryland Court of Appeals.

Justice Stevens

delivered the opinion of the Court.

A Massachusetts pricing order imposes an assessment on all fluid milk sold by dealers to Massachusetts retailers. About two-thirds of that milk is produced out of State. The entire assessment, however, is distributed to Massachusetts dairy farmers. The question presented is whether the pricing order unconstitutionally discriminates against interstate commerce. We hold that it does.

I

Petitioner West Lynn Creamery, Inc., is a milk dealer licensed to do business in Massachusetts. It purchases raw milk, which it processes, packages, and sells to wholesalers, retailers, and other milk dealers. About 97% of the raw milk it purchases is produced by out-of-state farmers. Petitioner LeComte’s Dairy, Inc., is also a licensed Massachusetts milk dealer. It purchases all of its milk from West Lynn and distributes it to retail outlets in Massachusetts.

Since 1937, the Agricultural Marketing Agreement Act, 50 Stat. 246, as amended, 7 U. S. C. § 601 et seq., has authorized the Secretary of Agriculture to regulate the minimum prices *189paid to producers of raw milk by issuing marketing orders for particular geographic areas.1 While the Federal Government sets minimum prices based on local conditions, those prices have not been so high as to prevent substantial competition among producers in different States. In the 1980’s and early 1990’s, Massachusetts dairy farmers began to lose market share to lower cost producers in neighboring States. In response, the Governor of Massachusetts appointed a Special Commission to study the dairy industry. The commission found that many producers had sold their dairy farms during the past decade and that if prices paid to farmers for their milk were not significantly increased, a majority of the remaining farmers in Massachusetts would be “forced out of business within the year.” App. 13. On January 28, 1992, relying on the commission’s report, the Commissioner of the Massachusetts Department of Food and Agriculture (respondent) declared a State of Emergency. *190In his declaration he noted that the average federal blend price2 had declined from $14.67 per hundred pounds (cwt) of raw milk in 1990 to $12.64/cwt in 1991, while costs of production for Massachusetts farmers had risen to an estimated average of $15.50/cwt. Id., at 27. He concluded:

“Regionally, the industry is in serious trouble and ultimately, a federal solution will be required. In the meantime, we must act on the state level to preserve our local industry, maintain reasonable minimum prices for the dairy farmers, thereby ensure a continuous and adequate supply of fresh milk for our market, and protect the public health.” Id., at 31.

Promptly after his declaration of emergency, respondent issued the pricing order that is challenged in this proceeding.3

The order requires every “dealer”4 in Massachusetts to make a monthly “premium payment” into the “Massachusetts Dairy Equalization Fund.” The amount of those payments is computed in two steps. First, the monthly “order premium” is determined by subtracting the federal blend price for that month from $15 and dividing the difference by three; thus if the federal price is $12/cwt, the order premium is $l/cwt.5 Second, the premium is multiplied by the amount *191(in pounds) of the dealer’s Class 16 sales in Massachusetts. Each month the fund is distributed to Massachusetts producers.7 Each Massachusetts producer receives a share of the total fund equal to his proportionate contribution to the State’s total production of raw milk.8

Petitioners West Lynn and LeComte’s complied with the pricing order for two months, paying almost $200,000 into the Massachusetts Dairy Equalization Fund. Id., at 100, 105. Starting in July 1992, however, petitioners refused to make the premium payments, and respondent commenced license revocation proceedings. Petitioners then filed an action in state court seeking an injunction against enforcement of the order on the ground that it violated the Commerce Clause of the Federal Constitution. The state court denied relief and respondent conditionally revoked their licenses.

The parties agreed to an expedited appellate procedure, and the Supreme Judicial Court of Massachusetts transferred the cases to its own docket. It affirmed, because it concluded that “the pricing order does not discriminate on its face, is evenhanded in its application, and. only incidentally *192burdens interstate commerce.” West Lynn Creamery, Inc. v. Commissioner of Dept. of Food and Agriculture, 415 Mass. 8, 15, 611 N. E. 2d 239, 243 (1993). The court noted that the “pricing order was designed to aid only Massachusetts producers.” Id., at 16, 611 N. E. 2d, at 244. It conceded that “[c]ommon sense” indicated that the plan has an “adverse impact on interstate commerce” and that “[t]he fund distribution scheme does burden out-of-State producers.” Id., at 17, 611 N. E. 2d, at 244. Nevertheless, the court asserted that “the burden is incidental given the purpose and design of the program.” Id., at 18, 611 N. E. 2d, at 244. Because it found that the “local benefits” provided to the Commonwealth’s dairy industry “outweigh any incidental burden on interstate commerce,” it sustained the constitutionality of the pricing order. Id., at 19, 611 N. E. 2d, at 245. We granted certiorari, 510 U. S. 811 (1993), and now reverse.

II

The Commerce Clause vests Congress with ample power to enact legislation providing for the regulation of prices paid to farmers for their products. United States v. Darby, 312 U. S. 100 (1941); Wickard v. Filburn, 317 U. S. 111 (1942); Mandeville Island Farms, Inc. v. American Crystal Sugar Co., 334 U. S. 219 (1948). An affirmative exercise of that power led to the promulgation of the federal order setting minimum milk prices. The Commerce Clause also limits the power of the Commonwealth of Massachusetts to adopt regulations that discriminate against interstate commerce. “This ‘negative’ aspect of the Commerce Clause prohibits economic protectionism — that is, regulatory measures designed to benefit in-state economic interests by burdening out-of-state competitors.... Thus, state statutes that clearly discriminate against interstate commerce are routinely struck down . . . unless the discrimination is demonstrably justified by a valid factor unrelated to economic protection*193ism . . . .” New Energy Co. of Ind. v. Limbach, 486 U. S. 269, 273-274 (1988).9

The paradigmatic example of a law discriminating against interstate commerce is the protective tariff or customs duty, which taxes goods imported from other States, but does not tax similar products produced in State. A tariff is an attractive measure because it simultaneously raises revenue and benefits local producers by burdening their out-of-state competitors. Nevertheless, it violates the principle of the unitary national market by handicapping out-of-state competitors, thus artificially encouraging in-state production even when the same goods could be produced at lower cost in other States.

Because of their distorting effects on the geography of production, tariffs have long been recognized as violative of the Commerce Clause. In fact, tariffs against the products of other States are so patently unconstitutional that our cases reveal not a single attempt by any State to enact one. Instead, the cases are filled with state laws that aspire to reap some of the benefits of tariffs by other means. In Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511 (1935), the State of New York attempted to protect its dairy farmers from the adverse effects of Vermont competition by establishing a single minimum price for all milk, whether produced in New York or elsewhere. This Court did not hesitate, however, to strike it down. Writing for a unanimous Court, Justice Cardozo reasoned:

*194“Neither the power to tax nor the police power may be used by the state of destination with the aim and effect of establishing an economic barrier against competition with the products of another state or the labor of its residents. Restrictions so contrived are an unreasonable clog upon the mobility of commerce. They set up what is equivalent to a rampart of customs duties designed to neutralize advantages belonging to the place of origin.” Id., at 527.

Thus, because the minimum price regulation had the same effect as a tariff or customs duty — neutralizing the advantage possessed by lower cost out-of-state producers — it was held unconstitutional. Similarly, in Bacchus Imports, Ltd. v. Dias, 468 U. S. 263 (1984), this Court invalidated a law which advantaged local production by granting a tax exemption to certain liquors produced in Hawaii. Other cases of this kind are legion. Welton v. Missouri, 91 U. S. 275 (1876); Guy v. Baltimore, 100 U. S. 434 (1880); Toomer v. Witsell, 334 U. S. 385 (1948); Polar Ice Cream & Creamery Co. v. Andrews, 375 U. S. 361 (1964); Chemical Waste Management, Inc. v. Hunt, 504 U. S. 334 (1992); see also Hunt v. Washington State Apple Advertising Comm’n, 432 U. S. 333, 351 (1977) (invalidating statute, because it “has the effect of stripping away from the Washington apple industry the competitive and economic advantages it has earned”).

Under these cases, Massachusetts’ pricing order is clearly unconstitutional. Its avowed purpose and its undisputed effect are to enable higher cost Massachusetts dairy farmers to compete with lower cost dairy farmers in other States. The “premium payments” are effectively a tax which makes milk produced out of State more expensive. Although the tax also applies to milk produced in Massachusetts, its effect on Massachusetts producers is entirely (indeed more than) offset by the subsidy provided exclusively to Massachusetts dairy farmers. Like an ordinary tariff, the tax is thus effectively imposed only on out-of-state products. The pricing *195order thus allows Massachusetts dairy farmers who produce at higher cost to sell at or below the price charged by lower cost out-of-state producers.10 If there were no federal minimum prices for milk, out-of-state producers might still be able to retain their market share by lowering their prices. Nevertheless, out-of-staters’ ability to remain competitive by lowering their prices would not immunize a discriminatory measure. New Energy Co. of Ind. v. Limbach, 486 U. S., at 275.11 In this case, because the Federal Government sets *196minimum prices, out-of-state producers may not even have the option of reducing prices in order to retain market share. The Massachusetts pricing order thus will almost certainly “cause local goods to constitute a larger share, and goods with an out-of-state source to constitute a smaller share, of the total sales in the market.”12 Exxon Corp. v. Governor of Maryland, 437 U. S. 117, 126, n. 16 (1978). In fact, this effect was the motive behind the promulgation of the pricing order. This effect renders the program unconstitutional, because it, like a tariff, “neutralizes] advantages belonging to the place of origin.” Baldwin, 294 U. S., at 527.

In some ways, the Massachusetts pricing order is most similar to the law at issue in Bacchus Imports, Ltd. v. Dias, 468 U. S. 263 (1984). Both involve a broad-based tax on a single kind of good and special provisions for in-state produc*197ers. Bacchus involved a 20% excise tax on all liquor sales, coupled with an exemption for fruit wine manufactured in Hawaii and for okolehao, a brandy distilled from the root of a shrub indigenous to Hawaii. The Court held that Hawaii’s law was unconstitutional because it “had both the purpose and effect of discriminating in favor of local products.” Id., at 273. See also I. M. Darnell & Son Co. v. Memphis, 208 U. S. 113 (1908) (invalidating property tax exemption favoring local manufacturers). By granting a tax exemption for local products, Hawaii in effect created a protective tariff. Goods produced out of State were taxed, but those produced in State were subject to no net tax. It is obvious that the result in Bacchus would have been the same if instead of exempting certain Hawaiian liquors from tax, Hawaii had rebated the amount of tax collected from the sale of those liquors. See New Energy Co. of Ind. v. Limbach, 486 U. S. 269 (1988) (discriminatory tax credit). And if a discriminatory tax rebate is unconstitutional, Massachusetts’ pricing order is surely invalid; for Massachusetts not only rebates to domestic milk producers the tax paid on the sale of Massachusetts milk, but also the tax paid on the sale of milk produced elsewhere.13 The additional rebate of the tax paid on the sale of milk produced elsewhere in no way reduces the danger to the national market posed by tariff-like barriers, but instead exacerbates the danger by giving domestic producers an additional tool with which to shore up their competitive position.14

*198III

Respondent advances four arguments against the conclusion that its pricing order imposes an unconstitutional burden on interstate commerce: (A) Because each component of the program — a local subsidy and a nondiscriminatory tax— is valid, the combination of the two is equally valid; (B) The dealers who pay the order premiums (the tax) are not competitors of the farmers who receive disbursements from the Dairy Equalization Fund, so the pricing order is not discriminatory; (C) The pricing order is not protectionist, because the costs of the program are borne only by Massachusetts dealers and consumers, and the benefits are distributed exclusively to Massachusetts farmers; and (D) The order’s incidental burden on commerce is justified by the local benefit of saving the dairy industry from collapse. We discuss each of these arguments in turn.

A

Respondent’s principal argument is that, because “the milk order achieves its goals through lawful means,” the order as a whole is constitutional. Brief for Respondent 20. He argues that the payments to Massachusetts dairy farmers from the Dairy Equalization Fund are valid, because subsidies are constitutional exercises of state power, and that the order premium which provides money for the fund is valid, because it is a nondiscriminatory tax. Therefore the pricing order is constitutional, because it is merely the combination of two independently lawful regulations. In effect, respondent argues, if the State may impose a valid tax on dealers, it is free to use the proceeds of the tax as it chooses; and *199if it may independently subsidize its farmers, it is free to finance the subsidy by means of any legitimate tax.

Even granting respondent’s assertion that both components of the pricing order would be constitutional standing alone,15 the pricing order nevertheless must fall. A pure subsidy funded out of general revenue ordinarily imposes no burden on interstate commerce, but merely assists local business. The pricing order in this case, however, is funded principally from taxes on the sale of milk produced in other States.16 By so funding the subsidy, respondent not only assists local farmers, but burdens interstate commerce. The pricing order thus violates the cardinal principle that a State may not “benefit in-state economic interests by burdening out-of-state competitors.” New Energy Co. of Ind. v. Limbach, 486 U. S., at 273-274; see also Bacchus Imports, Ltd. v. Dias, 468 U. S., at 272; Guy v. Baltimore, 100 U. S., at 443.

More fundamentally, respondent errs in assuming that the constitutionality of the pricing order follows logically from the constitutionality of its component parts. By conjoining *200a tax and a subsidy, Massachusetts has created a program more dangerous to interstate commerce than either part alone. Nondiscriminatory measures, like the evenhanded tax at issue here, are generally upheld, in spite of any adverse effects on interstate commerce, in part because “[t]he existence of major in-state interests adversely affected . . . is a powerful safeguard against legislative abuse.” Minnesota v. Clover Leaf Creamery Co., 449 U. S. 456, 473, n. 17 (1981); see also Raymond Motor Transp., Inc. v. Rice, 434 U. S. 429, 444, n. 18 (1978) (special deference to state highway regulations because “their burden usually falls on local economic interests as well as other States’ economic interests, thus insuring that a State’s own political processes will serve as a check against unduly burdensome regulations”); South Carolina Highway Dept. v. Barnwell Brothers, Inc., 303 U. S. 177, 187 (1938); Goldberg v. Sweet, 488 U. S. 252, 266 (1989).17 However, when a nondiscriminatory tax is coupled with a subsidy to one of the groups hurt by the tax, a State’s political processes can no longer be relied upon to prevent legislative abuse, because one of the in-state interests which would otherwise lobby against the tax has been mollified by the subsidy. So, in this case, one would ordinarily have expected at least three groups to lobby against the order premium, which, as a tax, raises the price (and hence lowers demand) for milk: dairy farmers, milk dealers, and consumers. But because the tax was coupled with a subsidy, one of the most powerful of these groups, Massachusetts dairy *201farmers, instead of exerting their influence against the tax, were in fact its primary supporters.18

Respondent’s argument would require us to analyze separately two parts of an integrated regulation, but we cannot divorce the premium payments from the use to which the payments are put. It is the entire program — not just the contributions to the fund or the distributions from that fund — that simultaneously burdens interstate commerce and discriminates in favor of local producers. The choice of constitutional means — nondiscriminatory tax and local subsidy — cannot guarantee the constitutionality of the program as a whole. New York’s minimum price order also used constitutional means — a State’s power to regulate prices — but was held unconstitutional because of its deleterious effects. Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511 (1935). Similarly, the law held unconstitutional in Bacchus Imports, Ltd. v. Dias, 468 U. S. 263 (1984), involved the exercise of Hawaii’s undisputed power to tax and to grant tax exemptions.

Our Commerce Clause jurisprudence is not so rigid as to be controlled by the form by which a State erects barriers to commerce. Rather our cases have eschewed formalism for a sensitive, case-by-case analysis , of purposes and effects. As the Court declared over 50 years ago: “The commerce clause forbids discrimination, whether forthright or ingenious. In each case it is our duty to determine whether the statute under attack, whatever its name may be, will in its practical operation work discrimination against interstate commerce.” Best & Co. v. Maxwell, 311 U. S. 454, 455-456 (1940); Maryland v. Louisiana, 451 U. S. 725, 756 (1981); *202 Exxon Corp. v. Governor of Maryland, 437 U. S., at 147; see also Guy v. Baltimore, 100 U. S., at 443 (invalidating discriminatory wharfage fees which were “mere expedient or device to accomplish, by indirection, what the State could not accomplish by a direct tax, viz., build up its domestic commerce by means of unequal and oppressive burdens upon the industry and business of other States”); Baldwin v. G. A. F. Seelig, Inc., 294 U. S., at 527 (“What is ultimate is the principle that one state in its dealings with another may not put itself in a position of economic isolation. Formulas and catchwords are subordinate to this overmastering requirement”); Dean Milk Co. v. Madison, 340 U. S. 349, 354 (1951); New Energy Co. of Ind. v. Limbach, 486 U. S., at 275, 276 (invalidating reciprocal tax credit because it, “in effect, tax[es] a product made by [Indiana] manufacturers at a rate higher than the same product made by Ohio manufacturers”).

B

Respondent also argues that since the Massachusetts milk dealers who pay the order premiums are not competitors of the Massachusetts farmers, the pricing order imposes no discriminatory burden on commerce. Brief for Respondent 28-29. This argument cannot withstand scrutiny. Is it possible to doubt that if Massachusetts imposed a higher sales tax on milk produced in Maine than milk produced in Massachusetts that the tax would be struck down, in spite of the fact that the sales tax was imposed on consumers, and consumers •do not compete with dairy farmers? For over 150 years, our cases have rightly concluded that the imposition of a differential burden on any part of the stream of commerce — from wholesaler to retailer to consumer — is invalid, because a burden placed at any point will result in a disadvantage to the out-of-state producer. Brown v. Maryland, 12 Wheat. 419, 444, 448 (1827) (“So, a tax on the occupation of an importer is, in like manner, a tax on importation. It must add to. the price of the article, and be paid by the consumer, or by the *203importer himself, in like manner as a direct duty on the article itself would be made.” “The distinction between a tax on the thing imported, and on the person of the importer, can have no influence on this part of the subject. It is too obvious for controversy, that they interfere equally with the power to regulate commerce”); I. M. Darnell & Son Co. v. Memphis, 208 U. S. 113 (1908) (differential burden on intermediate stage manufacturer); Bacchus Imports, Ltd. v. Dias, 468 U. S. 263 (1984) (differential burden on wholesaler); Webber v. Virginia, 103 U. S. 344, 350 (1881) (differential burden on sales agent); New Energy Co. of Ind. v. Limbach, 486 U. S., at 273-274 (differential burden on retailer).

C

Respondent also argues that “the operation of the Order disproves any claim of protectionism,” because “only in-state consumers feel the effect of any retail price increase . . . [and] [t]he dealers themselves ... have a substantial in-state presence.” Brief for Respondent 17 (emphasis in original). This argument, if accepted, would undermine almost every discriminatory tax case. State taxes are ordinarily paid by in-state businesses and consumers, yet if they discriminate against out-of-state products, they aré unconstitutional. The idea that a discriminatory tax does not interfere with interstate commerce “merely because the burden of the tax was borne by consumers” in the taxing State was thoroughly repudiated in Bacchus Imports, Ltd. v. Dias, 468 U. S., at 272. The cost of a tariff is also borne primarily by local consumers, yet a tariff is the paradigmatic Commerce Clause violation.

More fundamentally, respondent ignores the fact that Massachusetts dairy farmers are part of an integrated interstate market. As noted supra, at 194-196, the purpose and effect of the pricing order are to divert market share to Massachusetts dairy farmers. This diversion necessarily injures the dairy farmers in neighboring States. Further*204more, the Massachusetts order regulates a portion of the same interstate market in milk that is more broadly regulated by a federal milk marketing order which covers most of New England. 7 CFR § 1001.2 (1993). The Massachusetts producers who deliver milk to dealers in that regulated market are participants in the same interstate milk market as the out-of-state producers who sell in the same market and are guaranteed the same minimum blend price by the federal order. The fact that the Massachusetts order imposes assessments only on Massachusetts sales and distributes them only to Massachusetts producers does not exclude either the assessments or the payments from the interstate market. To the extent that those assessments affect the relative volume of Class I milk products sold in the marketing area as compared to other classes of milk products, they necessarily affect the blend price payable even to out-of-state producers who sell only in non-Massachusetts markets.19 The obvious impact of the order on out-of-state production demonstrates that it is simply wrong to assume that the pricing order burdens only Massachusetts consumers and dealers.

D

Finally, respondent argues that any incidental burden on interstate commerce “is outweighed by the ‘local benefits’ of preserving the Massachusetts dairy industry.”20 Brief for *205Respondent 42. In a closely related argument, respondent urges that “the purpose of the order, to save an industry from collapse, is not protectionist.” Id., at 16. If we were to accept these arguments, we would make a virtue of the vice that the rule against discrimination condemns. Preservation of local industry by protecting it from the rigors of interstate competition is the hallmark of the economic protectionism that the Commerce Clause prohibits. In Bacchus Imports, Ltd. v. Dias, 468 U. S., at 272, we explicitly rejected any distinction “between thriving and struggling enterprises.” Whether a State is attempting to “‘enhance thriving and substantial business enterprises’ ” or to “ ‘subsidize ... financially troubled’ ” ones is irrelevant to Commerce Clause analysis. Ibid. With his characteristic eloquence, Justice Cardozo responded to an argument that respondent echoes today:

“The argument is pressed upon us, however, that the end to be served by the Milk Control Act is something more than the economic welfare of the farmers or of any other class or classes. The end to be served is the maintenance of a regular and adequate supply of pure and wholesome milk, the supply being put in jeopardy when *206the farmers of the state are unable to earn a living income. Nebbia v. New York, [291 U. S. 502 (1934)] . . . Let such an exception be admitted, and all that a state will have to do in times of stress and strain is to say that its farmers and merchants and workmen must be protected against competition from without, lest they go upon the poor relief lists or perish altogether. To give entrance to that excuse would be to invite a speedy end of our national solidarity. The Constitution was framed under the dominion of a political philosophy less parochial in range. It was framed upon the theory that the peoples of the several states must sink or swim together, and that in the long run prosperity and salvation are in union and not division.” Baldwin v. G. A. F. Seelig, Inc., 294 U. S., at 522-523.21

In a later case, also involving the welfare of Massachusetts dairy farmers,22 Justice Jackson described the same overriding interest in the free flow of commerce across state lines:

“Our system, fostered by the Commerce Clause, is that every farmer and every craftsman shall be encouraged *207to produce by the certainty that he will have free access to every market in the Nation, that no home embargoes will withhold his exports, and no foreign state will by customs duties or regulations exclude them. Likewise, every consumer may look to the free competition from every producing area in the Nation to protect him from exploitation by any. Such was the vision of the Founders; such has been the doctrine of this Court which has given it reality.” H. P. Hood & Sons, Inc. v. Du Mond, 336 U. S. 525, 539 (1949).

The judgment of the Supreme Judicial Court of Massachusetts is reversed.

It is so ordered.

Justice Scalia, with whom Justice Thomas joins, concurring in the judgment.

In my view the challenged Massachusetts pricing order is invalid under our negative-Commerce-Clause jurisprudence, for the reasons explained in Part II below. I do not agree with the reasons assigned by the Court, which seem to me, as explained in Part I, a broad expansion of current law. Accordingly, I concur only in the judgment of the Court.

I

The purpose of the negative Commerce Clause, we have often said, is to create a national market. It does not follow from that, however, and we have never held, that every state law which obstructs a national market violates the Commerce Clause. Yet that is what the Court says today. It seems to have canvassed the entire corpus of negative-Commerce-Clause opinions, culled out every free-market snippet of reasoning, and melded them into the sweeping principle that the Constitution is violated by any state law or regulation that “artificially encourag[es] in-state production even when the same goods could be produced at lower cost in other States.” Ante, at 193. See also ante, at 194 (the *208law here is unconstitutional because it “neutralizes] the advantage possessed by lower cost out-of-state producers”); ante, at 195 (price order is unconstitutional because it allows in-state producers “who produce at higher cost to sell at or below the price charged by lower cost out-of-state producers”); ante, at 196 (a state program is unconstitutional where it “‘neutralizes advantages belonging to the place of origin’ ”) (quoting Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511, 527 (1935)); ante, at 205 (“Preservation of local industry by protecting it from the rigors of interstate competition is the hallmark of the economic protectionism that the Commerce Clause prohibits”).

As the Court seems to appreciate by its eagerness expressly to reserve the question of the constitutionality of subsidies for in-state industry, ante, at 199, and n. 15, this expansive view of the Commerce Clause calls into question a wide variety of state laws that have hitherto been thought permissible. It seems to me that a state subsidy would clearly be invalid under any formulation of the Court’s guiding principle identified above. The Court guardedly asserts that a “pure subsidy funded out of general revenue ordinarily imposes no burden on interstate commerce, but merely assists local business,” ante, at 199 (emphasis added), but under its analysis that must be taken to be true only because most local businesses (e. g., the local hardware store) are not competing with businesses out of State. The Court notes that, in funding this subsidy, Massachusetts has taxed milk produced in other States, and thus “not only assists local farmers, but burdens interstate commerce.” Ibid. But the same could be said of almost all subsidies funded from general state revenues, which almost invariably include moneys from use taxes on out-of-state products. And even where the funding does not come in any part from taxes on out-of-state goods, “merely assisting] ” in-state businesses, ibid., unquestionably neutralizes advantages possessed by out-of-state enterprises. Such subsidies, particularly where *209they are in the form of cash or (what comes to the same thing) tax forgiveness, are often admitted to have as their purpose — indeed, are nationally advertised as having as their purpose — making it more profitable to conduct business in State than elsewhere, i. e., distorting normal market incentives.

The Court’s guiding principle also appears to call into question many garden-variety state laws heretofore permissible under the negative Commerce Clause. A state law, for example, which requires, contrary to the industry practice, the use of recyclable packaging materials, favors local non-exporting producers, who do not have to establish an additional, separate packaging operation for in-state sales. If the Court’s analysis is to be believed, such a law would be unconstitutional without regard to whether disruption of the “national market” is the real purpose of the restriction, and without the need to “balance” the importance of the state interests thereby pursued, see Pike v. Bruce Church, Inc., 397 U. S. 137 (1970). These results would greatly extend the negative Commerce Clause beyond its current scope. If the Court does not intend these consequences, and does not want to foster needless litigation concerning them, it should not have adopted its expansive rationale. Another basis for deciding the case is available, which I proceed to discuss.

II

“The historical record provides no grounds for reading the Commerce Clause to be other than what it says — an authorization for Congress to regulate commerce.” Tyler Pipe Industries, Inc. v. Washington State Dept. of Revenue, 483 U. S. 232, 263 (1987) (Scalia, J., concurring in part and dissenting in part). Nonetheless, we formally adopted the doctrine of the negative Commerce Clause 121 years ago, see Case of the State Freight Tax, 15 Wall. 232 (1873), and since then have decided a vast number of negative-Commerce-Clause cases, engendering considerable reliance interests. *210As a result, I will, on stare decisis grounds, enforce a self-executing “negative” Commerce Clause in two situations: (1) against a state law that facially discriminates against interstate commerce, and (2) against a state law that is indistinguishable from a type of law previously held unconstitutional by this Court. See Itel Containers Int’l Corp. v. Huddleston, 507 U. S. 60, 78-79, and nn. 1, 2 (1993) (Scalia, J., concurring in judgment) (collecting cases). Applying this approach — or at least the second part of it — is not always easy, since once one gets beyond facial discrimination our negative-Commerce-Clause jurisprudence becomes (and long has been) a “quagmire.” Northwestern States Portland Cement Co. v. Minnesota, 358 U. S. 450, 458 (1959). See generally D. Currie, The Constitution in the Supreme Court: The First Hundred Years 1789-1888, pp. 168-181, 222-236, 330-342, 403-416 (1985). The object should be, however, to produce a clear rule that honors the holdings of our past decisions but declines to extend the rationale that produced those decisions any further. See American Trucking Assns., Inc. v. Scheiner, 483 U. S. 266, 305-306 (1987) (Scalia, J., dissenting).

There are at least four possible devices that would enable a State to produce the economic effect that Massachusetts has produced here: (1) a discriminatory tax upon the industry, imposing a higher liability on out-of-state members than on their in-state competitors; (2) a tax upon the industry that is nondiscriminatory in its assessment, but that has an “exemption” or “credit” for in-state members; (3) a nondiscriminatory tax upon the industry, the revenues from which are placed into a segregated fund, which fund is disbursed as “rebates” or “subsidies” to in-state members of the industry (the situation at issue in this case); and (4) with or without nondiscriminatory taxation of the industry, a subsidy for the in-state members of the industry, funded from the State’s general revenues. It is long settled that the first of these methodologies is unconstitutional under the negative Com*211merce Clause. See, e. g., Guy v. Baltimore, 100 U. S. 434, 443 (1880). The second of them, “exemption” from or “credit” against a “neutral” tax, is no different in principle from the first, and has likewise been held invalid. See Maryland v. Louisiana, 451 U. S. 725, 756 (1981); Westinghouse Elec. Corp. v. Tully, 466 U. S. 388, 399-400, and n. 9 (1984). The fourth methodology, application of a state subsidy from general revenues, is so far removed from what we have hitherto held to be unconstitutional, that prohibiting it must be regarded as an extension of our negative-Commerce-Clause jurisprudence and therefore, to me, unacceptable. See New Energy Co. of Ind. v. Limbach, 486 U. S. 269, 278 (1988). Indeed, in my view our negative-Commerce-Clause cases have already approved the use of such subsidies. See Hughes v. Alexandria Scrap Corp., 426 U. S. 794, 809-810 (1976).

The issue before us in the present case is whether the third of these methodologies must fall. Although the question is close, I conclude it would not be a principled point at which to disembark from the negative-Commerce-Clause train. The only difference between methodology (2) (discriminatory “exemption” from nondiscriminatory tax) and methodology (3) (discriminatory refund of nondiscriminatory tax) is that the money is taken and returned rather than simply left with the favored in-state taxpayer in the first place. The difference between (3) and (4), on the other hand, is the difference between assisting in-state industry through-discriminatory taxation and assisting in-state industry by other means.

I would therefore allow a State to subsidize its domestic industry so long as it does so from nondiscriminatory taxes that go into the State’s general revenue fund. Perhaps, as some commentators contend, that line comports with an important economic reality: A State is less likely to maintain a subsidy when its citizens perceive that the money (in the general fimd) is available for any number of competing, *212nonprotectionist, purposes. See Coenen, Untangling the Market-Participant Exemption to the Dormant Commerce Clause, 88 Mich. L. Rev. 395, 479 (1989); Collins, Economic Union as a Constitutional Value, 63 N. Y. U. L. Rev. 43, 103 (1988); Gergen, The Selfish State and the Market, 66 Texas L. Rev. 1097, 1138 (1988); see also ante, at 200, and n. 17. That is not, however, the basis for my position, for as The Chief Justice explains, “[ajnalysis of interest group participation in the political process may serve many useful purposes, but serving as a basis for interpreting the dormant Commerce Clause is not one of them.” Post, at 215 (dissenting opinion). Instead, I draw the line where I do because it is a clear, rational line at the limits of our extant negative-Commerce-Clause jurisprudence.

Chief Justice Rehnquist,

with whom Justice Black-MUN joins, dissenting.

The Court is less than just in its description of the reasons which lay behind the Massachusetts law which it strikes down. The law undoubtedly sought to aid struggling Massachusetts dairy farmers, beset by steady or declining prices and escalating costs. This situation is apparently not unique to Massachusetts; New Jersey has filed an amicus brief in support of respondent because New Jersey has enacted a similar law. Both States lie in the northeastern metropolitan corridor, which is the most urbanized area in the United States, and has every prospect of becoming more so. The value of agricultural land located near metropolitan areas is driven up by the demand for housing and similar urban uses; distressed farmers eventually sell out to developers. Not merely farm produce is lost, as is the milk production in this case, but, as the Massachusetts Special Commission whose report was the basis for the order in question here found:

“Without the continued existence of dairy farmers, the Commonwealth will lose its supply of locally produced fresh milk, together with the open lands that are used as *213wildlife refuges, for recreation, hunting, fishing, tourism, and education.” App. 13.

Massachusetts has dealt with this problem by providing a subsidy to aid its beleaguered dairy farmers. In case after case, we have approved the validity under the Commerce Clause of such enactments. “No one disputes that a State may enact laws pursuant to its police powers that have the purpose and effect of encouraging domestic industry.” Bacchus Imports, Ltd. v. Dias, 468 U. S. 263, 271 (1984). “Direct subsidization of domestic industry does not ordinarily run afoul of [the dormant Commerce Clause]; discriminatory taxation of out-of-state manufacturers does.” New Energy Co. of Ind. v. Limbach, 486 U. S. 269, 278 (1988). But today the Court relegates these well-established principles to a footnote and, at the same time, gratuitously casts doubt on the validity of state subsidies, observing that “[w]e have never squarely confronted” their constitutionality. Ante, at 199, n. 15.

But in Milk Control Bd. v. Eisenberg Farm Products, 306 U. S. 346 (1939), the Court upheld a Pennsylvania statute establishing minimum prices to be paid to Pennsylvania dairy farmers against a Commerce Clause challenge by a Pennsylvania milk dealer that shipped all of its milk purchased in Pennsylvania to New York to be sold there. The Court observed that “[t]he purpose of the statute ... is to reach a domestic situation in the interest of the welfare of the producers and consumers of milk in Pennsylvania.” Id., at 352. It went on to say:

“One of the commonest forms of state action is the exercise of the police power directed to the control of local conditions and exerted in the interest of the welfare of the state’s citizens. Every state police statute necessarily will affect interstate commerce in some degree, but such a statute does not run counter to the grant of Congressional power merely because it incidentally or *214indirectly involves or burdens interstate commerce. ... These principles have guided judicial decision for more than a century.” Id., at 351-352.

The Massachusetts subsidy under consideration is similar in many respects to the Pennsylvania statute described in Eisenberg, supra. Massachusetts taxes all dealers of milk within its borders. The tax is evenhanded on its face, i. e., it affects all dealers regardless of the point of origin of the milk. Ante, at 194 (“the tax also applies to milk produced in Massachusetts”); ante, at 200 (“the evenhanded tax at issue here”). The State has not acted to strong-arm sister States as in Limbaeh; rather, its motives are purely local. As the Supreme Judicial Court of Massachusetts aptly described it: “[T]he premiums represent one of the costs of doing business in the Commonwealth, a cost all milk dealers must pay.” West Lynn Creamery, Inc. v. Commissioner of Dept. of Food and Agriculture, 415 Mass. 8, 19, 611 N. E. 2d 239, 245 (1993).

Consistent with precedent, the Court observes: “A pure subsidy funded out of general revenue ordinarily imposes no burden on interstate commerce, but merely assists local business.” Ante, at 199. And the Court correctly recognizes that “[njondiscriminatory measures, like the evenhanded tax at issue here, are generally upheld” due to the deference normally accorded to a State’s political process in passing legislation in light of various competing interest groups. Ante, at 200, citing Minnesota v. Clover Leaf Creamery Co., 449 U. S. 456, 473, n. 17 (1981), and Raymond Motor Transp., Inc. v. Rice, 434 U. S. 429, 444, n. 18 (1978). But the Court strikes down this method of state subsidization because the nondiscriminatory tax levied against all milk dealers is coupled with a subsidy to milk producers. Ante, at 200-201. The Court does this because of its view that the method of imposing the tax and subsidy distorts the State’s political process: The dairy farmers, who would otherwise lobby against the tax, have been mollified by the subsidy. Ibid. But as the Court itself points out, there are still at least two *215strong interest groups opposed to the milk order — consumers and milk dealers. More importantly, nothing in the dormant Commerce Clause suggests that the fate of state regulation should turn upon the particular lawful manner in which the state subsidy is enacted or promulgated. Analysis of interest group participation in the political process may serve many useful purposes, but serving as a basis for interpreting the dormant Commerce Clause is not one of them.

The Court concludes that the combined effect of the milk order “simultaneously burdens interstate commerce and discriminates in favor of local producers.” Ante, at 201. In support of this conclusion, the Court cites Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511 (1935), and Bacchus Imports, Ltd. v. Dias, supra, as two examples in which constitutional means were held to have unconstitutional effects on interstate commerce. But both Baldwin and Bacchus are a far cry from this case.

In Baldwin, supra, in order to sell bottled milk in New York, milk dealers were required to pay a minimum price for milk, even though they could have purchased milk from Vermont farmers at a lower price. This scheme was found to be an effort to prevent Vermont milk producers from selling to New York dealers at their lower market price. As Justice Cardozo explained, under the New York statute, “the importer... may keep his milk or drink it, but sell it he may not.” 294 U. S., at 521. Such a scheme clearly made it less attractive for New York dealers to purchase milk from Vermont farmers, for the disputed law negated any economic advantage in so doing. Under the Massachusetts milk order, there is no such adverse effect. Milk dealers have the same incentives to purchase lower priced milk from out-of-state farmers; dealers of all milk are taxed equally. To borrow Justice Cardozo’s description, milk dealers in Massachusetts are free to keep their milk, drink their milk, and sell it — on equal terms as local milk.

*216In Bacchus, the State of Hawaii combined its undisputed power to tax and grant exemptions in a manner that the Court found violative of the Commerce Clause. There, the State exempted a local wine from the burdens of an excise tax levied on all other liquor sales. Despite the Court’s strained attempt to compare the scheme in Bacchus to the milk order in this case, ante, at 196-197, it is clear that the milk order does not produce the same effect on interstate commerce as the tax exemption in Bacchus. I agree with the Court’s statement that Bacchus can be distinguished “by noting that the rebate in this case goes not to the entity which pays the tax (milk dealers) but to the dairy farmers themselves.” Ante, at 197, n. 14. This is not only a distinction, but a significant difference. No decided case supports the Court’s conclusion that the negative Commerce Clause prohibits the State from using money that it has lawfully obtained through a neutral tax on milk dealers and distributing it as a subsidy to dairy farmers. Indeed, the case which comes closest to supporting the result the Court reaches is the ill-starred opinion in United States v. Butler, 297 U. S. 1 (1936), in which the Court held unconstitutional what would have been an otherwise valid tax on the processing of agricultural products because of the use to which the revenue raised by the tax was put.

More than half a century ago, Justice Brandéis said in his dissenting opinion in New State Ice Co. v. Liebmann, 285 U. S. 262, 311 (1932):

“To stay experimentation in things social and economic is a grave responsibility. Denial of the right to experiment may be fraught with serious consequences to the Nation. It is one of the happy incidents of the federal system that a single courageous State may, if its citizens choose, serve as a laboratory; and try novel social and economic experiments without risk to the rest of the country.”

*217Justice Brandéis’ statement has been cited more than once in subsequent majority opinions of the Court. See, e.g., Reeves, Inc. v. Stake, 447 U. S. 429, 441 (1980). His observation bears heeding today, as it did when he made it. The wisdom of a messianic insistence on a grim sink-or-swim policy of laissez-faire economics would be debatable had Congress chosen to enact it; but Congress has done nothing of the kind. It is the Court which has imposed the policy under the dormant Commerce Clause, a policy which bodes ill for the values of federalism which have long animated our constitutional jurisprudence.