A 1924 act permitted Indian tribes to lease mineral rights on their reservation land. The 1924 act explicitly permitted states to tax royalty payments the tribes received under those leases. In 1938, Congress passed the Indian Mineral Leasing Act of 1938. The 1938 act did not explicitly permit state taxation of royalty payments, nor did it explicitly repeal the provision of the 1924 act permitting such taxation. However, the 1938 act contained a general clause repealing all prior laws inconsistent with the 1938 act. The Blackfeet Tribe of Indians (the tribe) (defendants) leased oil and gas rights on reservation land to non-Indians. The state of Montana (plaintiff) sought to tax the tribe’s royalty payments under those leases.