The Constitution does not give Indian tribes any sovereign rights. The Constitution, Art. I, §8, cl. 3, gives the federal government plenary authority over Indian affairs. Montana v. Blackfeet Tribe, 471 U.S. 759, 764-765 (1985). Congressional law is therefore the source of whatever rights Indian tribes possess, and Congress may restrict or modify those rights as it chooses. For example, in Escondido Mutual Water Co. v. La Jolla Band of Mission Indians, 466 U.S. 765, 787 n.30 (1984), an Indian tribe argued that a federal agency could not issue hydroelectric power licenses on reservation land without the Tribe's consent. The Court rejected this argument: "[I]t is clear that all aspects of Indian sovereignty are subject to defeasance by Congress. . .and Congress intended to [regulate the issuance of hydroelectric licenses on Indian lands] without the consent of the tribes involved." 466 U.S. at 787 n.30.

This means that the federal government has the power to regulate or tax Indian enterprises, whether on or off the reservation. Superintendent of Five Civilized Tribes v. Commissioner of Internal Revenue, 295 U.S. 418, 421 (1935)(income tax for on reservationland); Escondido Mutual Water, 466 U.S. at 787 n.30 (hydroelectric power license for reservation lands); Wheeler, 435 U.S. at 330-331 (unrestricted federal jurisdiction to define and punish crimes on reservation land, notwithstanding tribal court rulings on same charges).

The tribes are therefore recognized to be not independent units of government. They are "dependents" of the United States. Duro v. Reina, 495 U.S.676, 686 (1990) ("dependent status") Oliphant v. Suquamish Indian Tribe, 435 U.S. 191, 196 (1978)  "