A Crow tribal police officer approached Joshua Cooley’s truck on a public highway within the Crow Reservation after observing that Cooley appeared non-Native and had watery, bloodshot eyes. The officer temporarily detained Cooley, looked inside the truck, saw weapons and drug paraphernalia, and contacted federal authorities. Cooley argued that the officer lacked authority to detain and search a non-Indian on tribal land. The Supreme Court held that tribal police retain authority to detain temporarily and search a non-Indian traveling on a public right-of-way when the officer has reasonable suspicion that the person has violated state or federal law. The rule is a narrow authority to investigate and protect public safety, not general tribal criminal jurisdiction over non-Indians. The Court concluded that the officer’s observations justified the initial detention and protective search and rejected the contrary Ninth Circuit rule. It vacated the judgment and remanded.