Colorado River Water Conservation District v. United States

In reading this case, it helps to know four things.  First, there is a statute that provides federal district courts with subject matter jurisdiction over any lawsuit in which the United States is a party.  You are not responsible for this statute; for your purposes, it operates just like § 1331, for which you are responsible. Second, the doctrine of sovereign immunity precludes suits against the United States (there are certain exceptions, including one allowing suits for injunctions against allegedly unconstitutional federal action); Congress has the power to waive sovereign immunity by statute, but ordinarily, unless it has done so, no suit against the United States will lie.  Third, the federal government often acts on behalf of Indian tribes, either formally as a “trustee” or informally as a protector or asserter of their rights.  The federal government is seen as less hostile to Native American interests than state governments.  Fourth, the federal government at one time owned a great deal of the land that now constitutes the western portion of the United States.  It sold or granted most of this land to people or entities that would use it in accordance with the government’s wishes, usually by living on it or otherwise developing it.  In these grants, the federal government would sometimes “reserve” rights corresponding to the land, including some water rights.