This article is a content analysis examination of 107 federal court cases involving American Indian tribal sovereignty and federal pleary power rendered between 1870 and 1921. Our focus, however, is the U.S. Supreme Court's Indian Law jurisprudence; thus ninety of the cases analyzed were Supreme Court opinions. The cases seemingly entail two separate braces of opinions. One brace included decisions which affirmed tribal sovereignty. The other brace entailed cases which negatively affected tribal sovereignty. These negative decisions generally relied on doctrines such as plenary power, the political question doctrine, or the so- called "guardian-ward" relationship. We argue that the Supreme Court, as a partner in the ruling national alliance, generally deferred to the legislative branches during this critical historical era, Indian treaties and extra- constitutional rights notwithstanding. In seeking to explain the two separate, though not unrelated sets of opinions, we focus on the Court's role in formulating public policy towards American Indian tribes in four major issue areas: congressional power, criminal law, allotment and membership, and natural resources. And we attempt to explain how and why the Court's perception of these issues were transformed over time and how these changes affected tribal sovereign rights. Finally, we develop a synthetic, abstract model of judicial decision-making which provides some explanatory power regarding why the Court decides Indian related issues the way it does.