In the United States v. Dion case of 1985, the Supreme Court ruled that members of federally recognized tribes do not have treaty rights to hunt or sell parts of endangered species unless explicitly stated in their treaties with the federal government. The case involved a member of the Yankton Sioux Tribe, Dwight Dion Sr., who was charged for selling bald eagle parts in violation of federal law protecting endangered species. Despite his argument that he had an inherent tribal right to take eagles as part of traditional religious ceremonies and thus could legally sell them, the court held that such rights were subject to regulation by Congress under its plenary power over Indian affairs. Therefore, without explicit protection from a treaty provision exempting him from compliance with general laws applicable to all citizens - which did not exist in this instance - Dion's actions were deemed illegal.

In the dissenting opinion for United States v. Dion, Justice Brennan disagreed with the majority's interpretation of a federal statute that allowed Native Americans to hunt bald and golden eagles for religious purposes. He argued that this law should be interpreted more broadly to protect tribal rights, rather than narrowly as the majority had done. Brennan contended that Congress did not intend to abrogate treaty rights without clear intent, which he believed was absent in this case. He also pointed out inconsistencies in how similar laws were applied to different tribes, suggesting an unfair application of justice. Furthermore, he criticized the court's reliance on legislative history instead of focusing on statutory language or congressional intent when interpreting laws affecting tribal sovereignty and hunting rights.