The Supreme Court established three principles to measure Congress's intent to diminish a reservation. It decided that opening up reservation lands for settlement by non-Indians does not constitute the intent to diminish reservation boundaries and therefore reservation boundaries would not be diminished unless specifically determined through legislation. Decided February 22, 1984 (argued December 6, 1983). Opinion of the Court: Thurgood Marshall → go there Topic: Native American law. Solem v. Bartlett, 465 U.S. 463 (1984), was a United States Supreme Court case involving Indian country jurisdiction in the United States that decided that opening up reservation lands for settlement by non-Indians does not constitute the intent to diminish reservation boundaries. Therefore, reservation boundaries would not be diminished unless specifically determined through acts of Congress. Wiki link