On June 1, 2021, the Supreme Court unanimously held that a tribal police officer does have authority to temporarily detain and search non-Indians traveling on public rights-of-way running through a reservation. United States v. Cooley, ___ U.S. ___, No. 19-1414. The tribal police officer may investigate potential violations of state or federal law during such a stop, not just violations of tribal law.

Cooley, a non-Indian, was in a truck parked on the side of a highway within the boundaries of the Crow Reservation in Montana. A tribal police officer spotted Cooley and asked him why he was parked on the side of the highway in the middle of the night. The officer observed two semi-automatic rifles and a pistol in the truck. The officer called for backup from the county police and secured Cooley in his patrol car. While securing the weapons, the officer saw methamphetamine in the vehicle.

In the District Court, Cooley successfully moved to suppress the evidence on the theory that the officer acted outside the scope of his authority as a tribal law enforcement officer in detaining Cooley. A Ninth Circuit panel affirmed.

In a unanimous decision written by Justice Breyer, the Court noted the “general proposition that the inherent sovereign powers of an Indian tribe do not extend to the activities of nonmembers of the tribe.” Slip. Op. at 4 (citing Montana v. United States, 450 U.S. 544 (1981)). However, the court emphasized that the rule was not absolute and that two exceptions exist. First, a tribe “may regulate, through taxation, licensing, or other means, the activities of nonmembers who enter consensual relationships with the tribe or its members, through commercial dealing, contracts, leases or other arrangements.” Id. Second, a “tribe may also retain inherent power to exercise civil authority over the conduct of non-Indians on fee lands within its reservation when that conduct threatens or has some direct effect on the political integrity, the economic security, or
the health or welfare of the tribe.”

Holding that the second exception “fits the present case, almost like a glove” the Court upheld the authority of tribal police to detain non-Indians traveling on public rights of way through a reservation. The Court quoted the Washington Supreme Court’s holding in another case that “[a]llowing a known drunk driver to get back in his or her car, careen off down the road, and possibly kill or injure Indians or non-Indians would certainly be detrimental to the health or welfare of the Tribe.” Id. at 5 (quoting State v. Schmuck, 850 P.2d 1332, 1341, cert. denied, 510 U.S. 931 (1993)). The Court also expressed concerns about the practical consequences of the
Ninth Circuit’s holding for the safety of Indians and non-Indians living on Indian reservations, citing amicus briefs filed former U.S. Attorneys and the National Indigenous Women’s Resource Center.

The Court’s reaffirmation of the first exception to Montana’s general proposition may also prove to be useful to tribes engaged in economic development efforts that involve contracting with non-Indian persons. Justice Alito concurred stating he would limit the holding to cases in which the public highway is “primarily patrolled” by tribal police.