United States v. Cooley

Although the Montana rule generally precludes tribal jurisdiction over non-Indians on public roads within a reservation, the Court recognized an exception for inherent sovereign authority necessary to maintain law and order and protect tribal self-governance. Here, the tribal officer's detention of Cooley satisfied this exception because he had reasonable suspicion that Cooley was violating federal drug and weapons laws, conduct that directly threatens tribal public safety and the integrity of the reservation community. The detainment of a non-Indian on a public highway was therefore valid when conducted pursuant to the tribe's core function of enforcing law and transferring violators to appropriate federal or state authorities.