Snell & Wilmer[co-author: Kelsey Haake1]

On June 1, in a landmark case, the U.S. Supreme Court declared unanimously that tribal police officers have the authority to temporarily detain and search non-Natives on public rights-of-way through Indian lands if they are suspected of violating federal or state law. This ruling is significant for Indian Country as it solidifies rights by tribes to exercise their sovereignty while removing previous limitations.

In United States v. Cooley , which involved a tribal police officer’s search and seizure authority, the Court reversed the Ninth Circuit Court of Appeals’ ruling that tribal safety patrol officers lacked the power to detain and search the defendant, Joshua James Cooley, because he was a non-Native. Cooley was initially arrested on tribal lands after an officer searched his vehicle, where evidence was found leading to a federal drug and firearms possession charge.

Cooley moved to suppress the evidence found in the search, arguing the tribal police officer lacked the authority to investigate and detain him because he is a non-Native. The Ninth Circuit agreed and ruled in favor of Cooley.

In overturning the Ninth Circuit, the Supreme Court based its decision on the long-standing Federal Indian Law precedent of United States v. Montana , stating that tribes do not have jurisdiction over non-Natives on reservations unless their behavior “threatens or has some direct effect on the political integrity, the economic security, or the health or welfare of the tribe.” The power to detain and investigate non-Natives on highways running through tribal lands would be an exercise of this authority to protect their community against any threats to their health and welfare.

Justice Stephen Breyer wrote the opinion and stated that it “would make it difficult for tribes to protect themselves against ongoing threats” such as “non-Native drunk drivers, transporters of contraband, or other criminal offenders operating on roads within the boundaries of a tribal reservation.”

Arguably, the most significant piece of Justice Breyer’s opinion is that the charges Cooley faced were not tribal allegations, but under “state and federal laws that apply whether an individual is outside a reservation or on a state or federal highway within it.” Meaning, there now appears to be precedent in place authorizing tribal police officers to investigate and temporarily detain non-Native motorists if there is suspicion of state and federal crimes – and not simply alleged violations of tribal law.

Justice Alito wrote a one-paragraph concurrence clarifying when tribal police officers have authority on public rights-of-way. Essentially, he wrote tribal officers have the power to stop non-Natives if the officer:

1) Has a “reasonable suspicion that the motorist may violate or has violated federal or state law.”

2) If the search was necessary to protect themselves or others.

3) If the officer has probable cause to detain the motorist until a non-tribal officer arrives on the scene.

The Cooley decision is important for tribes to continue acting in a sovereign capacity and to further protect their tribal lands. Ultimately, this gives tribes the power to have the most significant impact on the safety of their lands and those who live and travel within their boundaries.


  1. Kelsey Haake is a 2021 Summer Associate at Snell & Wilmer, and is a 2023 JD Candidate at the University of Pennsylvania Carey School of Law.
  2. United States v. Cooley, 593 U.S. __(2021).
  3. Montana v. United States, 450 U.S. 544 (1981).