The State of Washington (defendant) imposed a tax on the sale of cigarettes. The tax did not apply to cigarettes sold by Indians on a reservation to other members of the tribe. Several Indian tribes (Tribes) (plaintiffs) regularly sold cigarettes on reservation to non-Indians, charging only a tribal tax. Washington demanded that the Tribes collect taxes due the state. When the Tribes refused to collect the tax, Washington intercepted and confiscated shipments of cigarettes en route to the reservation. The Tribes sued, seeking declaratory and injunctive relief against imposition of the tax and seizure of the cigarettes. The Tribes claimed that Washington’s cigarette tax was preempted by federal law and inconsistent with tribal self-governance (the taxes would cause the Tribes to lose a significant, competitive, economic advantage). The district court entered judgment for the Tribes, holding that state taxation of the cigarettes on reservation was preempted by the tribal taxing ordinance and improperly interfered with tribal self-governance. The United States Supreme Court granted certiorari.