Mr. Justice Powell

delivered the opinion of the Court.

This case brings before us a constitutional challenge to §§ 101 (b) (1) (D) and 101 (b) (2) of the Immigration and Nationality Act of 1952 (Act), 66 Stat. 182, as amended, 8 U. S. C. §§ 1101 (b) (1) (D) and 1101 (b) (2).

I

The Act grants special preference immigration status to aliens who qualify as the “children” or “parents” of United States citizens or lawful permanent residents. Under § 101 (b) (1), a “child” is defined as an unmarried person under 21 years of age who is a legitimate or legitimated child, a stepchild, an adopted child, or an illegitimate child seeking preference by virtue of his relationship with his natural mother.1 *789The definition does not extend to an illegitimate child seeking preference by virtue of his relationship with his natural father. Moreover, under § 101 (b) (2), a person qualifies as a “parent” for purposes of the Act solely on the basis of the person’s relationship with a “child.” As a result, the natural father of an illegitimate child who is either a United States citizen or permanent resident alien is not entitled to preferential treatment as a “parent.”

The special preference immigration status provided for those who satisfy the statutory “parent-child” relationship depends on whether the immigrant’s relative is a United States citizen or permanent resident alien. A United States citizen is allowed the entry of his “parent” or “child” without regard to either an applicable numerical quota or the labor certification requirement. 8 U. S. C. §§ 1151 (a), (b), 1182 (a) (14). On the other hand, a United States permanent resident alien is allowed the entry of the “parent” or “child” subject to numerical limitations but without regard to the labor certifi*790cation requirement. 8 U. S. C. § 1182 (a) (14); see 1 C. Gordon & H. Rosenfield, Immigration Law and Procedure § 2.40 n. 18 (rev. ed. 1975).2

Appellants are three sets of unwed natural fathers and their illegitimate offspring who sought, either as an alien father or an alien child, a special immigration preference by virtue of a relationship to a citizen or resident alien child or parent. In each instance the applicant was informed that he was ineligible for an immigrant visa unless he qualified for admission under the general numerical limitations and, in the case of the alien parents, received the requisite labor certification.3

*791Appellants filed this action in July 1974 in the United States District Court for the Eastern District of New York challenging the constitutionality of §§ 101 (b)(1) and 101 (b) (2) of the Act under the First, Fifth, and Ninth Amendments. Appellants alleged that the statutory provisions (i) denied them equal protection by discriminating against natural fathers and their illegitimate children “on the basis of the father’s marital status, the illegitimacy of the child and the sex of the parent without either compelling or rational justification”; (ii) denied them due process of law to the extent that there was established “an unwarranted conclusive presumption of the absence of strong psychological and economic ties between natural fathers and their children born out of wedlock and not legitimated”; and (iii) “seriously burden[ed] and infringe [d] upon the rights of natural fathers and their children, born out of wedlock and not legitimated, to mutual association, to privacy, to establish a home, to raise natural children and to be raised by the natural father.” App. 11-12. Appellants sought to enjoin permanently enforcement of the challenged statutory provisions to the extent that the statute precluded them from qualifying for the special preference accorded other “parents” and “children.”

A three-judge District Court was convened to consider the constitutional issues. After noting that Congress’ power to fashion rules for the admission of aliens was “exceptionally broad,” the District Court held, with one judge dissenting, that the statutory provisions at issue were neither “wholly devoid of any conceivable rational purpose” nor “fundamentally aimed at achieving a goal unrelated to the regulation of immigration.” Fiallo v. Levi, 406 F. Supp. 162, 165, 166 *792(1975). The court therefore granted judgment for the Government and dismissed the action.

We noted probable jurisdiction sub nom. Fiallo v. Levi, 426 U. S. 919 (1976), and for the reasons set forth below we affirm.

II

At the outset, it is important to underscore the limited scope of judicial inquiry into immigration legislation. This Court has repeatedly emphasized that “over no conceivable subject is the legislative power of Congress more complete than it is over” the admission of aliens. Oceanic Navigation Co. v. Stranahan, 214 U. S. 320, 339 (1909); accord, Kleindienst v. Mandel, 408 U. S. 753, 766 (1972). Our cases “have long recognized the power to expel or exclude aliens as a fundamental sovereign attribute exercised by the Government's political departments largely immune from judicial control.” Shaughnessy v. Mezei, 345 U. S. 206, 210 (1953); see, e. g., Harisiades v. Shaughnessy, 342 U. S. 580 (1952); Lem Moon Sing v. United States, 158 U. S. 538 (1895); Fong Yue Ting v. United States, 149 U. S. 698 (1893); The Chinese Exclusion Case, 130 U. S. 581 (1889). Our recent decisions have not departed from this long-established rule. Just last Term, for example, the Court had occasion to note that “the power over aliens is of a political character and therefore subject only to narrow judicial review.” Hampton v. Mow Sun Wong, 426 U. S. 88, 101 n. 21 (1976), citing Fong Yue Ting v. United States, supra, at 713; accord, Mathews v. Diaz, 426 U. S. 67, 81-82 (1976). And we observed recently that in the exercise of its broad power over immigration and naturalization, “Congress regularly makes rules that would be unacceptable if applied to citizens.” Id., at 80.4

*793Appellants apparently do not challenge the need for special judicial deference to congressional policy choices in the immigration context,5 but instead suggest that a “unique coalescing of factors” makes the instant case sufficiently unlike prior immigration cases to warrant more searching judicial scrutiny. Brief for Appellants 52-55. Appellants first observe that since the statutory provisions were designed to reunite families wherever possible, the purpose of the statute was to afford rights not to aliens but to United States citizens and legal permanent residents. Appellants then rely on our border-search decisions in Almeida-Sanchez v. United States, 413 U. S. 266 (1973), and United States v. Brignoni-Ponce, 422 U. S. 873 (1975), for the proposition that the courts must *794scrutinize congressional legislation in the immigration area to protect against violations of the rights of citizens. At issue in the border-search cases, however, was the nature of the protections mandated by the Fourth Amendment with respect to Government procedures designed to stem the illegal entry of aliens. Nothing in the opinions in those cases suggests that Congress has anything but exceptionally broad power to determine which classes of aliens may lawfully enter the country. See 413 U. S., at 272; 422 U. S., at 883-884.

Appellants suggest a second distinguishing factor. They argue that none of the prior immigration cases of this Court involved “double-barreled” discrimination based on sex and illegitimacy, infringed upon the due process rights of citizens and legal permanent residents, or implicated “the fundamental constitutional interests of United States citizens and permanent residents in a familial relationship.” Brief for Appellants 53-54; see id., at 16-18. But this Court has resolved similar challenges to immigration legislation based on other constitutional rights of citizens, and has rejected the suggestion that more searching judicial scrutiny is required. In Kleindienst v. Mandel, supra, for example, United States citizens challenged the power of the Attorney General to deny a visa to an alien who, as a proponent of “the economic, international, and governmental doctrines of World communism,” was ineligible to receive a visa under 8 U. S. C. § 1182 (a) (28) (D) absent a waiver by the Attorney General. The citizen-appellees in that case conceded that Congress could prohibit entry of all aliens falling into the class defined by § 1182 (a) (28) (D). They contended, however, that the Attorney General’s statutory discretion to approve a waiver was limited by the Constitution and that their First Amendment rights were abridged by the denial of Mandel’s request for a visa. The Court held that “when the Executive exercises this [delegated] power negatively on the basis of a facially legitimate and bona fide reason, the courts will neither look behind *795the exercise of that discretion, nor test it by balancing its justification against the First Amendment interests of those who seek personal communication with the applicant.” 408 U. S., at 770. We can see no reason to review the broad congressional policy choice at issue here under a more exacting standard than was applied in Kleindienst v. Mandel, a First Amendment case.6

*796Finally, appellants characterize our prior immigration cases as involving foreign policy matters and congressional choices to exclude or expel groups of aliens that were “specifically and clearly perceived to pose a grave threat to the national security,” citing Harisiades v. Shaughnessy, 342 U. S. 580 (1952), “or to the general welfare of this country,” citing Boutilier v. INS, 387 U. S. 118 (1967). Brief for Appellants 54. We find no indication in our prior cases that the scope of judicial review is a function of the nature of the policy choice at issue. To the contrary, “[s]ince decisions in these matters may implicate our relations with foreign powers, and since a wide variety of classifications must be defined in the light of changing political and economic circumstances, such decisions are frequently of a character more appropriate to either the Legislature or the Executive than to the Judiciary,” and “[t]he reasons that preclude judicial review of political questions also dictate a narrow standard of review of decisions made by the Congress or the President in the area of immigration and naturalization.” Mathews v. Diaz, 426 U. S., at 81-82. See Harisiades v. Shaughnessy, supra, at 588-589. As Mr. Justice Frankfurter observed in his concurrence in Harisiades v. Shaughnessy:

“The conditions of entry for every alien, the particular classes of aliens that shall be denied entry altogether, the basis for determining such classification, the right to terminate hospitality to aliens, the grounds on which such determination shall be based, have been recognized as matters solely for the responsibility of the Congress and wholly outside the power of this Court to control.” 342 U. S., at 596-597.

*797III

As originally enacted in 1952, §101 (b) (1) of the Act defined a “child” as an unmarried legitimate or legitimated child or stepchild under 21 years of age. The Board of Immigration Appeals and the Attorney General subsequently concluded that the failure of this definition to refer to illegitimate children rendered ineligible for preferential nonquota status both the illegitimate alien child of a citizen mother, Matter of A, 5 I. & N. Dec. 272, 283-284 (A. G. 1953), and the alien mother of a citizen born out of wedlock, Matter of F, 7 I. & N. Dec. 448 (B. I. A. 1957). The Attorney General recommended that the matter be brought to the attention of Congress, Matter of A, supra, at 284, and the Act was amended in 1957 to include what is now 8 U. S. C. § 1101 (b) (1) (D). See n. 1, supra. Congress was specifically concerned with the relationship between a child born out of wedlock and his or her natural mother, and the legislative history of the 1957 amendment reflects an intentional choice not to provide preferential immigration status by virtue of the relationship between an illegitimate child and his or her natural father.7

This distinction is just one of many drawn by Congress pursuant to its determination to provide some—but not all—families with relief from various immigration restrictions that would otherwise hinder reunification of the family in this country. In addition to the distinction at issue here, Con*798gress has decided that children, whether legitimate or not, cannot qualify for preferential status if they are married or are over 21 years of age. 8 U. S. C. § 1101 (b) (1). Legitimated children are ineligible for preferential status unless their legitimation occurred prior to their 18th birthday and at a time when they were in the legal custody of the legitimating parent or parents. § 1101 (b) (1) (C). Adopted children are not entitled to preferential status unless they were adopted before the age of 14 and have thereafter lived in the custody of their adopting or adopted parents for at least two years, § 1101 (b) (1) (E). And stepchildren cannot qualify unless they were under 18 at the time of the marriage creating the stepchild relationship. § 1101 (b) (1) (B).

With respect to each of these legislative policy distinctions, it could be argued that the line should have been drawn at a different point and that the statutory definitions deny preferential status to parents and children who share strong family ties. Cf. Mathews v. Diaz, supra, at 83-84. But it is clear from our cases, see Part II, supra, that these are policy questions entrusted exclusively to the political branches of our Government, and we have no judicial authority to substitute our political judgment for that of the Congress.

Appellants suggest that the distinction drawn in § 101 (b) (1) (D) is unconstitutional under any standard of review since it infringes upon the constitutional rights of citizens and legal permanent residents without furthering legitimate governmental interests. Appellants note in this regard that the statute makes it more difficult for illegitimate children and their natural fathers to be reunited in this country than for legitimate or legitimated children and their parents, or for illegitimate children and their natural mothers. And appellants also note that the statute fails to establish a procedure under which illegitimate children and their natural fathers could prove the existence and strength of their family relationship. Those are admittedly the consequences of the *799congressional decision not to accord preferential status to this particular class of aliens, but the decision nonetheless remains one “solely for the responsibility of the Congress and wholly outside the power of this Court to control.” Harisiades v. Shaughnessy, 342 U. S., at 597 (Frankfurter, J., concurring). Congress obviously has determined that preferential status is not warranted for illegitimate children and their natural fathers, perhaps because of a perceived absence in most cases of close family ties as well as a concern with the serious problems of proof that usually lurk in paternity determinations.8 See Trimble v. Gordon, ante, at 771. In any event, it is not the judicial role in cases of this sort to probe and test the justifications for the legislative decision.9 Kleindienst v. Mandel, 408 U. S., at 770.

IV

We hold that §§ 101 (b) (1) (D) and 101 (b) (2) of the *800Immigration and Nationality Act of 1952 are not unconstitutional by virtue of the exclusion of the relationship between an illegitimate child and his natural father from the preferences accorded by the Act to the “child” or “parent” of a United States citizen or lawful permanent resident.

Affirmed.

Mr. Justice Marshall,

with whom Mr. Justice Brennan joins, dissenting.

Until today I thought it clear that when Congress grants benefits to some citizens, but not to others, it is our duty to insure that the decision comports with Fifth Amendment principles of due process and equal protection. Today, however, the Court appears to hold that discrimination among citizens, however invidious and irrational, must be tolerated if it occurs in the context of the immigration laws. Since I cannot agree that Congress has license to deny fundamental rights to citizens according to the most disfavored criteria simply because the Immigration and Nationality Act is involved, I dissent.

I

The Immigration and Nationality Act of 1952 (INA), 8 U. S. C. § 1101 et seq., establishes the terms and conditions for entry into the United States. Among its various conditions, the Act requires that an alien seeking to enter the United States as a legal permanent resident must come within a restrictive numerical quota and must satisfy certain labor certification requirements. INA §§201, 202, 212 (a) (14), 8 U. S. C. §§ 1151, 1152, 1182 (a) (14) (1976 ed.), as amended by the Immigration and Nationality Act Amendments of 1976, 90 Stat. 2703 (hereinafter 1976 Amendments). In recognition of the fact that such requirements frequently separate families, Congress has provided that American citizens may petition *801to have the requirements waived for their immediate families—spouse, parents, children. INA §§ 201 (a), (b), 212 (a) (14), 8 U. S. C. §§ 1151 (a), (b), 1182 (a) (14).1

*802The privilege is accorded only to those parents and children who satisfy the statute’s definitions. Under INA § 101 (b) (1), a “child” is defined as an unmarried person under 21 years of age who is a legitimate or legitimated child, a stepchild, an adopted child, or an illegitimate child by whom or on whose behalf a privilege is sought by virtue of the relationship of the child to its biological mother. 8 U. S. C. § 1101 (b) (1).2 A “parent” is defined under INA § 101 (b) (2) solely *803on the basis of the individual’s relationship with a “child” as defined by § 101 (b) (1). 8 U. S. C. § 1101 (b) (2).3 The definitions cover virtually all parent-child relationships except that of biological father-illegitimate child. Thus while all American citizens are entitled to bring in their alien children without regard to either the numerical quota or the labor certification requirement, fathers are denied this privilege with respect to their illegitimate children. Similarly, all citizens are allowed to have their parents enter without regard to the labor certification requirement, and, if the citizen is over 21, also without regard to the quota. Illegitimate children, however, are denied such preferences for their fathers.

The unfortunate consequences of these omissions are graphically illustrated by the case of appellant Cleophus Warner.4 *804Mr. Warner is a naturalized citizen of the United States who, pursuant to 8 U. S. C. § 1154,5 petitioned the Attorney General for an immigrant visa for his illegitimate son Serge, a citizen of the French West Indies. Despite the fact that Mr. Warner acknowledged his paternity and registered as Serge's father shortly after his birth, has his name on Serge's birth certificate, and has supported and maintained Serge since birth, the special dispensation from the quota and labor certification requirements was denied because Serge was not a “child” under the statute. It matters not that, as the Government concedes, Tr. of Oral Arg. 25-26, Serge’s mother has abandoned Serge to his father and has, by marrying another man, apparently rendered impossible, under French West Indies law, Mr. Warner’s ever legitimating Serge. Mr. Warner is simply not Serge’s “parent.”

II

The Government contends that this legislation is not subject to judicial review. Pointing to the fact that aliens have no constitutional right to immigrate to the United States and to a long line of cases that recognize that policies pertaining to *805the entry of aliens and their right to remain here are peculiarly concerned with the political conduct of government, the Government concludes that “[t]he congressional decision whether or to whom to extend such a valuable privilege . . . is not a subject of judicial concern.” Brief for Appellees 22.

The Court rightly rejects this expansive claim and recognizes that “[o]ur cases reflect acceptance of a limited judicial responsibility . . . even with respect to the power of Congress to regulate the admission and exclusion of aliens.” Ante, at 793 n. 5. It points out, however, that the scrutiny is circumscribed. Congress has “broad power to determine which classes of aliens may lawfully enter the country” and its political judgments warrant deference. Ante, at 794-796.

I wholeheartedly agree with the Court’s rejection of the Government’s claim of unreviewable discretion. Indeed, as I observed in Kleindienst v. Mandel, 408 U. S. 753, 781 (1972) (dissenting opinion), the old immigration cases that reflect an absolute “hands-off” approach by this Court “are not the strongest precedents in the United States Reports.” I am pleased to see the Court reveal once again a “reluctance to rely on them completely.” Ibid. I also have no quarrel with the principle that the essentially political judgments by Congress as to which foreigners may enter and which may not deserve deference from the judiciary.

My disagreement with the Court arises from its application of the principle in this case. The review the majority purports to require turns out to be completely “toothless.” Cf. Trimble v. Gordon, ante, at 767. After observing the effects of the denial of preferential status to appellants, the majority concludes: “[B]ut the decision nonetheless remains one 'solely for the responsibility of the Congress and wholly outside the power of this Court to control.’ ” Ante, at 799. Such “review” reflects more than due deference; it is abdication.6 *806Assuming, arguendo, that such deference might be appropriate in some situations—a supposition I find difficult to accept—it is particularly inappropriate in this case.

This case, unlike most immigration cases that come before the Court, directly involves the rights of citizens, not aliens. “[C] oncerned with the problem of keeping families of United States citizens and immigrants united,” H. R. Rep. No. 1199, 85th Cong., 1st Sess., 7 (1957), Congress extended to American citizens the right to choose to be reunited in the United States with their immediate families. The focus was on citizens and their need for relief from the hardships occasioned by the immigration laws. The right to seek such relief was given only to the citizen, not the alien. 8 U. S. C. § 1154.7 If the citizen does not petition the Attorney General for the special “immediate relative” status for his parent or child, the alien, *807despite his relationship, can receive no preference. 8 U. S. C. § 1153 (d). It is irrelevant that aliens have no constitutional right to immigrate and that Americans have no constitutional right to compel the admission of their families. The essential fact here is that Congress did choose to extend such privileges to American citizens but then denied them to a small class of citizens. When Congress draws such lines among citizens, the Constitution requires that the decision comport with Fifth Amendment principles of equal protection and due process. The simple fact that the discrimination is set in immigration legislation cannot insulate from scrutiny the invidious abridgment of citizens’ fundamental interests.

The majority responds that in Kleindienst v. Mandel, supra, the Court recognized that First Amendment rights of citizens were “implicated,” but refused to engage in the close scrutiny usually required in First Amendment cases. Therefore, it argues, no more exacting standard is required here. In that case, Mandel, a Belgian “revolutionary Marxist,” could visit this country only if the Attorney General waived the statutory prohibition of visas to “[a]liens who advocate the economic, international, and governmental doctrines of World communism.” 8 U. S. C. § 1182 (a) (28) (D). The Attorney General denied the waiver, and suit was brought by Mandel and several citizens who claimed their First Amendment right to hear Mandel in person was abridged by the denial. Rejecting the Government’s contention that it had “unfettered discretion, and any reason or no reason [for denying a waiver] may be given,” the Court upheld the denial only after finding that it was based on a “legitimate and bona fide” reason—Mandel’s abuses of visa privileges on a prior visit. 408 U. S., at 769. At the same time, however, the Court chose not to scrutinize more closely and accepted the reason without weighing against it the claimed First Amendment interest. It feared becoming embroiled in the “dangerous and undesirable” task of con*808sidering, every time an alien was denied a waiver, such factors as the projected number of people wishing to speak with the alien and the probity of his ideas. Id., at 769.

Whatever the merits of the Court’s fears in Mandel, cf. id., at 774 (Marshall, J., dissenting), the present case is clearly distinguishable in two essential respects. First, in Mandel, Congress had not focused on citizens and their need for relief. Rather, the governmental action was concerned with keeping out “undesirables.” The impact on the citizens’ right to hear was an incidental and unavoidable consequence of that political judgment. The present case presents a qualitatively different situation. Here, the purpose of the legislation is to accord rights, not to aliens, but to United States citizens. In so doing, Congress deliberately chose, for reasons unrelated to foreign policy concerns or threats to national security, to deny those rights to a class of citizens traditionally subject to discrimination.8 Second, in Mandel, unlike the present case, appellees conceded the ability of Congress to enact legislation broadly prohibiting the entry of all aliens with Mandel’s beliefs.9 Their concern was directed instead to the exercise of the discretion granted the Attorney General to waive the prohibition. In the present case, by contrast, we are asked to engage in the traditional task of reviewing the valid*809ity of a general Act of Congress challenged as unconstitutional on its face. Totally absent therefore is the specter of involving the courts in second-guessing countless individual determinations by the Attorney General as to the merits of a particular alien’s entrance.

III

A

Once it is established that this discrimination among citizens cannot escape traditional constitutional scrutiny simply because it occurs in the context of immigration legislation, the result is virtually foreordained. One can hardly imagine a more vulnerable statute.

The class of citizens denied the special privilege of reunification in this country is defined on the basis of two traditionally disfavored classifications—gender and legitimacy. Fathers cannot obtain preferred status for their illegitimate children; mothers can. Conversely, every child except the illegitimate—legitimate, legitimated, step-, adopted—can obtain preferred status for his or her alien father. The Court has little tolerance for either form of discrimination. We require that gender-based classifications “serve important governmental objectives and . . . be substantially related to achievement of those objectives.” Califano v. Webster, ante, at 317; Califano v. Goldfarb, ante, at 210-211; Craig v. Boren, 429 U. S. 190, 197 (1976); see also Weinberger v. Wiesenfeld, 420 U. S. 636 (1975); Stanton v. Stanton, 421 U. S. 7 (1975); Taylor v. Louisiana, 419 U. S. 522 (1975); Frontiero v. Richardson, 411 U. S. 677 (1973); Reed v. Reed, 404 U. S. 71 (1971). We are similarly hostile to legislation excluding illegitimates from governmental beneficence, finding it “illogical and unjust” to deprive a child “simply because its natural father has not married its mother.” Gomez v. Perez, 409 U. S. 535, 538 (1973). See also Trimble v. Gordon, ante, p. 762; Jimenez v. Weinberger, 417 U. S. 628 (1974); Beaty v. Weinberger, 478 F. 2d 300 (CA5 1973), summarily aff’d, 418 U. S. 901 (1974); *810 New Jersey Welfare Rights Org. v. Cahill, 411 U. S. 619 (1973); Weber v. Aetna Casualty & Surety Co., 406 U. S. 164 (1972); Davis v. Richardson, 342 F. Supp. 588 (Conn., 1972), summarily aff’d, 409 U. S. 1069 (1972); Griffin v. Richardson, 346 F. Supp. 1226 (Md.), summarily aff’d, 409 U. S. 1069 (1972); Glona v. American Guarantee Liability Ins. Co., 391 U. S. 73 (1968); Levy v. Louisiana, 391 U. S. 68 (1968); cf. Mathews v. Lucas, 427 U. S. 495 (1976). But see Labine v. Vincent, 401 U. S. 532 (1971).

But it is not simply the invidious classifications that make the statute so vulnerable to constitutional attack. In addition the statute interferes with the fundamental “freedom of personal choice in matters of marriage and family life.” Cleveland Board of Education v. LaFleur, 414 U. S. 632, 639-640 (1974); see also Roe v. Wade, 410 U. S. 133, 152-153 (1973); Wisconsin v. Yoder, 406 U. S. 205, 231-233 (1972); Stanley v. Illinois, 405 U. S. 645, 651 (1972); Ginsberg v. New York, 390 U. S. 629, 639 (1968); Griswold v. Connecticut, 381 U. S. 479 (1965); id., at 495-496 (Goldberg, J., concurring); id., at 502-503 (White, J., concurring); Poe v. Ullman, 367 U. S. 497, 542-544, 549-553 (Harlan, J., dissenting). The right to live together as a family belongs to both the child who seeks to bring in his or her father and the father who seeks the entrance of his child.

“It is no less important for a child to be cared for by its . . . parent when that parent is male rather than female. And a father, no less than a mother, has a constitutionally protected right to the 'companionship, care, custody, and management’ of 'the children he has sired and raised . . .’ Stanley v. Illinois, 405 U. S. 645, 651 (1972).” Weinberger v. Wiesenfeld, supra, at 652.

In view of the legislation’s denial of this right to these classes, it is clear that, whatever the verbal formula, the Government bears a substantial burden to justify the statute.

*811B

There is no dispute that the purpose of these special preference provisions is to reunify families separated by the immigration laws. As Congress itself declared “[t]he legislative history of the Immigration and Nationality Act clearly indicates that the Congress intended [in these provisions] to provide for a liberal treatment of children and was concerned with the problem of keeping families of United States citizens and immigrants united.” H. R. Rep. No. 1199, 85th Cong., 1st Sess., 7 (1957). It is also clear that when Congress extended the privilege to cover the illegitimate-child-mother relationship in 1957, it did so to alleviate hardships it found in several cases denying preferential status to illegitimate children and their mothers. Id., at 7-8. Accord, S. Rep. No. 1057, 85th Cong., 1st Sess., 4 (1957).

The legislative history, however, gives no indication of why these privileges were absolutely denied illegitimate children and their fathers.10 The Government suggests that Congress may have believed that “such persons are unlikely to have maintained a close personal relationship with their offspring.” Brief for Appellees 17. If so, Congress’ chosen shorthand for “closeness” is obviously overinclusive. No one can dispute that there are legitimate, legitimated, step-, and adoptive parent-child relationships and mother-illegitimate child relationships that are not close and yet are accorded the preferential status. Indeed, the most dramatic illustration of the overinclusiveness is the fact that while Mr. Warner can never be deemed a “parent” of Serge, nevertheless, if he should marry, his wife could qualify as a stepparent, entitled to obtain for Serge the preferential status that Mr. Warner cannot *812obtain. Andrade v. Esperdy, 270 F. Supp. 516 (SDNY 1967); Nation v. Esperdy, 239 F. Supp. 531 (SDNY 1965).11 Similarly, a man who, in an adulterous affair, fathers a child outside his marriage cannot be the “parent” of that child, but his wife may petition as stepparent. Matter of Stultz, 15 I. & N. Dec. — (1975).

That the statute is underinclusive is also undisputed. Brief for Appellees 17; Tr. of Oral Arg. 21. Indeed, the Government could not dispute it in view of the close relationships exhibited in appellants’ cases, recognized in our previous cases, see, e. g., Trimble v. Gordon, ante, p. 762; Weber v. Aetna Casualty & Surety Co., supra, at 169; Stanley v. Illinois, supra, and established in numerous studies.12

The Government suggests that Congress may have decided to accept the inaccurate classifications of this statute because they considered a case-by-case assessment of closeness and *813paternity not worth the administrative costs. This attempted justification is plainly inadequate. In Stanley v. Illinois, supra, we expressed our low regard for the use of “administrative convenience” as the rationale for interfering with a father’s right to care for his illegitimate child.

“Procedure by presumption is always cheaper and easier than individualized determination. But when, as here, the procedure forecloses the determinative issues of competence and care, when it explicitly disdains present realities in deference to past formalities, it needlessly risks running roughshod over the important interests of both parent and child. It therefore cannot stand.” 405 U. S., at 656-657.

See also Glona v. American Guarantee & Liability Ins. Co., supra.

This Court has been equally intolerant of the rationale when it is used to deny rights to the illegitimate child. While we are sensitive to “ 'the lurking problems with respect to proof of paternity,’ ” Trimble v. Gordon, ante, at 771, quoting Gomez v. Perez, 409 U. S. 535, 538 (1973), we are careful not to allow them to be “ 'made into an impenetrable barrier that works to shield otherwise invidious discrimination.’ ” Trimble, ante, at 771. We require, at a minimum, that the “ ‘statute [be] carefully tuned to alternative considerations,’ ” ante, at 772, quoting Mathews v. Lucas, 427 U. S., at 513, and not exclude all illegitimates simply because some situations involve difficulties of proof. Ibid.

Given such hostility to the administrative-convenience argument when invidious classifications and fundamental rights are involved, it is apparent that the rationale is inadequate in the present case. As I observed earlier, since Congress gave no indication that administrative costs were its concern we should scrutinize the hypothesis closely. The likelihood of such a rationale is diminished considerably by the comprehensive and elaborate administrative procedures *814already established and employed by the INS in passing on claims of the existence of a parent-child relationship. All petitions are handled on a case-by-case basis with the petitioner bearing the burden of proof. Moreover, the INS is no stranger to cases requiring proof of paternity. When, for example, a citizen stepmother petitions for the entrance of her husband’s illegitimate child, she must necessarily prove that her husband is the child’s father.13 Indeed, it is ironic that if Mr. Warner marries and his wife petitions for Serge, her proof will, in fact, be one step more complex than his would be—not only must she prove his paternity, but she must also prove their marriage. Nevertheless, she would be entitled to an opportunity to prove those facts; he is not.

Nor is a fear of involvement with foreign laws and records a persuasive explanation of the omission. In administering the Act with respect to legitimated children, for example, the critical issue is whether the steps undertaken are adequate under local law to render the child legitimate, and the INS has become expert in such matters.14 I note, in this connec*815tion, that where a child was born in a country in which all children are legitimate,15 proof of paternity is the critical issue and the proof problems are identical to those involved with an illegitimate child.

Given the existence of these procedures and expertise, it is difficult indeed to give much weight to the hypothesized administrative-convenience rationale. Moreover, as noted previously, this Court will not allow concerns with proof to justify “an impenetrable barrier that works to shield otherwise invidious discrimination.” Gomez, supra, at 538. As the facts of this case conclusively demonstrate, Congress has “failed to consider the possibility of a middle ground between the extremes of complete exclusion and case-by-case determination of paternity.” Trimble, ante, at 770-771. Mr. Warner is a classic example of someone who can readily prove both paternity and closeness. Appellees concede this. Tr. of Oral Arg. 21-22. The fact that he is denied the opportunity demonstrates beyond peradventure that Congress has failed to “‘carefully tun[e] [the statute] to alternative considerations.' ” Trimble, ante, at 772, quoting Mathews v. Lucas, 427 U. S., at 513. That failure is fatal to the statute. Trimble, ante, at 772-773.16

*816IV

When Congress grants a fundamental right to all but an invidiously selected class of citizens, and it is abundantly clear that such discrimination would be intolerable in any context but immigration, it is our duty to strike the legislation down. Because the Court condones the invidious discrimination in this case simply because it is embedded in the immigration laws, I must dissent.

Mr. Justice White also dissents, substantially for the reasons stated by Mr. Justice Marshall in his dissenting opinion.