In United States v. Cooley (2021), the U.S. Supreme Court ruled unanimously that an Indian tribe police officer has the authority to detain temporarily and search a non-Indian person traveling on a public right of way that runs through an Indian reservation. A police officer of Montana’s Crow Tribe had detained Joshua Cooley and searched his vehicle, which Cooley had stopped on the side of U.S. Route 212. The officer seized several guns and observed what he believed was methamphetamine. Cooley was formally arrested at the Crow Agency Police Department. Cooley sought to suppress the evidence in federal court on the ground that the police officer had no authority to detain and search a non-Indian on the U.S. highway. Writing for the Court, Associate Justice Stephen Breyer opined that a recognized tribe has inherent power to regulate the behavior of non-Indians on its reservation where that behavior “directly threatens or has some direct effect on the political integrity, the economic security, or the health and welfare of the tribe.”
Cooley was a major decision upholding what Breyer called tribes’ “retained inherent sovereign authority,” especially in the light of the Court’s tendencies in recent decades to reduce that sovereignty. However, the scope of tribal sovereignty remains very unclear.
Elizabeth Reese, “Affirmation of inherent tribal power to police blurs civil and criminal Indian law tests,” SCOTUSblog (Jun. 7, 2021, 10:29 PM), https://www.scotusblog.com/2021/06/affirmation-of-inherent-tribal-power-to-police-blurs-civil-and-criminal-indian-law-tests/