Oliphant, the first attempt in recent case law to deal directly with the issue of tribal criminal jurisdiction over non-Indians, represents an acceptance of the theory that tribal sovereignty is diminished only to the extent that it is expressly limited by the federal government. The Court of Appeals for the Ninth Circuit held that, in the absence of any express limitations on tribal power, the original criminal jurisdiction of the tribe remains undiminished. After establishing this foundational principle, the court proceeded to analyze the alleged limitations on tribal jurisdiction. First, the court found no treaty purporting to limit the tribe\u27s criminal jurisdiction. Second, the federal jurisdictional statute was found to contain no claim of exclusivity. Third, the court construed the 1968 Indian Civil Rights Act as limiting but not extinguishing tribal criminal jurisdiction over non-Indians. Fourth, state jurisdiction under Public Law 280 was found to have been effectively retroceded. Finally, the court found that tribal criminal jurisdiction over non-Indians conformed with the federal policy of encouraging Indian self-government
