The Neets’aii Gwich’in Tribe (Tribe) (respondent) was living in far northern Alaska on land initially set aside as an Indian reservation. In 1971, the federal government passed the Alaska Native Claims Settlement Act (ANCSA), 43 U.S.C. § 1601 et seq. The ANCSA sought to revoke the reservation status of the land and to transfer ownership and management of the land to state-chartered private corporations formed under the ANCSA and managed by the Native Alaskans. The reservation land was transferred to the Tribe in fee simple, without restriction. In 1986, the private corporations contracted to build a school on the land. The private corporations imposed taxes on the contractor and on the State of Alaska (petitioner), as a party to the agreement, for conducting business on tribal land. The State of Alaska sued to prevent the Tribe from collecting the tax. The State of Alaska argued that the Tribe was no longer a dependent Indian community under the Indian Country Act (ICA), 18 U.S.C. § 1151(b), and that the land of the Tribe was not Indian country on which the Tribe could impose a tax. The United States District Court for the District of Alaska ruled in favor of the State of Alaska and held that the land was not Indian country. The United States Court of Appeals for the Ninth Circuit reversed. The ninth circuit held that the land was Indian country. The United States Supreme Court granted certiorari.