United States v. Cooley

The Court began with Montana v. United States, which states the general rule that tribes ordinarily lack inherent sovereign authority over nonmembers’ activities. But Montana also recognizes an exception where nonmember conduct threatens, or directly affects, the tribe’s political integrity, economic security, health, or welfare. That second exception closely fits the authority at issue because a tribe cannot adequately protect its community if its officers must allow suspected drunk drivers, armed individuals, or contraband traffickers to continue operating on roads inside reservation boundaries.

Prior precedent supported this conclusion. In Strate v. A-1 Contractors, although the Court denied tribal-court jurisdiction over a civil suit arising from an accident on a state highway through a reservation, it specifically declined to question tribal police authority to patrol such roads, detain nonmembers who violate state law, and turn them over to state officers. Duro v. Reina likewise recognized that tribal officers may detain and transport offenders to the appropriate outside authorities when the tribe lacks power to prosecute them. The authority to conduct a safety-related search before transport is ancillary to that recognized detention authority.

The Court distinguished this limited policing authority from the broader exercises of tribal power over nonmembers that prior decisions had rejected. Cooley would not be tried under tribal law or subjected to tribal regulations in which he had no political voice. Instead, the tribal officer’s investigation concerned possible violations of state and federal law, laws that applied to Cooley regardless of whether he was on or off the reservation.

The Ninth Circuit’s proposed rules were also impractical. Requiring an officer first to ask about Indian status would invite false answers and would make an officer’s ability to respond to apparent danger turn on an unreliable initial inquiry. Requiring an “apparent” violation would introduce an unfamiliar and uncertain standard into search-and-seizure law, even though encounters between tribal officers and non-Indians are common on many reservations.

Cooley argued that statutes authorizing federal commissions and cross-deputization for tribal officers defined the permissible scope of tribal law enforcement and left no room for inherent authority beyond those arrangements. The Court disagreed because the cited provisions did not clearly address or withdraw the narrow authority at issue.

The federal framework was both overinclusive and underinclusive as a substitute for the inherent power recognized here. Some provisions encompass powers such as arrest, which the Court was not deciding, while they do not cover enforcement of state law. Requiring tribes to obtain separate agreements with federal, state, and local governments to address every public-safety threat would also make effective coverage difficult. Nothing in the statutes demonstrated a congressional purpose to deny tribes this retained authority; existing legislation and executive practice instead appeared to assume it exists.