Although, for many years, respondent Indian Tribe has sold cigarettes at a convenience store that it owns and operates in Oklahoma on land held in trust for it by the Federal Government, it has never collected Oklahomas cigarette tax on these sales. In 1987, petitioner, the Oklahoma Tax Commission (Oklahoma or Commission), served the Tribe with an assessment letter, demanding that it pay taxes on cigarette sales occurring between 1982 and 1986. The Tribe filed suit in the District Court to enjoin the assessment, and Oklahoma counterclaimed to enforce the assessment and to enjoin the Tribe from making future sales without collecting and remitting state taxes. The court refused to dismiss the counterclaims on the Tribes motion, which was based on the assertion that the Tribe had not waived its sovereign immunity from suit. The court held on the merits that the Commission lacked authority to tax on-reservation sales to tribal members or to tax the Tribe directly, and therefore that the Tribe was immune from Oklahomas suit to collect past unpaid taxes directly, but that the Tribe could be required to collect taxes prospectively for on-reservation sales to nonmembers. The Court of Appeals reversed, holding, inter alia, that the lower court erred in entertaining Oklahomas counterclaims because the Tribe enjoys absolute sovereign immunity from suit and had not waived that immunity by filing its action for injunctive relief, and that Oklahoma lacked authority to tax any on-reservation sales, whether to tribesmen or nonmembers.

Held:

Under the doctrine of tribal sovereign immunity, a State that has not asserted jurisdiction over Indian lands under Public Law 280 may not tax sales of goods to tribesmen occurring on land held in trust for a federally recognized Indian tribe, but is free to collect taxes on such sales to nonmembers of the tribe. Pp. 509-514.

(a) The Tribe did not waive its inherent sovereign immunity from suit merely by seeking an injunction against the Commissions proposed tax assessment. United States v. United States Fidelity and Guaranty Co., 309 U.S. 506, 511-512, 513. In light of this Courts reaffirmation, in a number of cases, of its longstanding doctrine of tribal sovereign immunity, and Congress consistent reiteration of its approval of the doctrine in order to promote Indian self-government, self-sufficiency, an [498 U.S. 505, 506] economic development, the Court is not disposed to modify or abandon the doctrine at this time. Nor is there merit to Oklahomas contention that immunity should not apply because the Tribes cigarette sales do not occur on a formally designated "reservation." Trust land qualifies as a reservation for tribal immunity purposes where, as here, it has been "validly set apart for the use of the Indians as such, under the superintendence of the Government." United States v. John, 437 U.S. 634, 648-649. Mescalero Apache Tribe v. Jones, 411 U.S. 145, 148-149, which approved nondiscriminatory state taxation of activities on non-reservation, nontrust Government land leased by Indians, is not to the contrary. Pp. 509-511.

(b) Nevertheless, the Tribes sovereign immunity does not deprive Oklahoma of the authority to tax cigarette sales to nonmembers of the Tribe at the Tribes store, and the Tribe has an obligation to assist in the collection of validly imposed state taxes on such sales. Moe v. Confederated Salish and Kootenai Tribes, 425 U.S. 463, 482, 483; Washington v. Confederated Tribes of Colville Reservation, 447 U.S. 134. This case is not distinguishable from Moe and Colville on the ground that Oklahoma disclaimed jurisdiction over Indian lands upon entering the Union and did not reassert jurisdiction over civil causes of action in such lands as permitted by Public Law 280. Neither of those cases depended on the assertion of such jurisdict