United States v. Cooley
The Supreme Court unanimously ruled that tribal police officers have the authority to stop, search, and briefly hold non-tribal members on public roads within a reservation when the officer suspects a violation of state or federal law.
The decision resolves a split among courts over how far tribal policing power extends and closes an enforcement gap that, under the Ninth Circuit's previous rules, could have required tribal officers to let potentially dangerous drivers go free.
How it got here: A federal district court suppressed the drug evidence; the Ninth Circuit affirmed; the federal government petitioned the Supreme Court, which agreed to hear the case.
The Case in Depth
What happened
A Crow Tribe police officer in Montana spotted a truck parked late at night on a U.S. highway running through the Crow Reservation. The driver appeared to be non-Native, had bloodshot eyes, and had two semiautomatic rifles on the front seat. The officer ordered him out, conducted a search, and found methamphetamine. A federal grand jury charged the driver with drug and weapons offenses, but the lower courts threw out the drug evidence, ruling that the tribal officer lacked authority to search a non-tribal member.
The question before the Court
Can a tribal police officer on a Native American reservation stop and search a non-tribal member driving on a public highway running through the reservation?
The Court's answer
Yes — a tribal police officer can stop, search, and temporarily hold a non-tribal member driving on a public road within a reservation when the officer suspects a state or federal law violation. The Court relied on a 1981 precedent, Montana v. United States, which recognized that tribes retain sovereign authority over non-members whose conduct threatens the health or welfare of the tribe. Allowing a non-tribal driver who appears drunk, armed, or carrying drugs to simply drive away would plainly threaten the tribe's safety and welfare.
The Court also rejected the Ninth Circuit's two-step rule, which required tribal officers first to determine whether a suspect was non-Indian before acting, and then allowed temporary detention only when a legal violation was "apparent." The Court found that rule unworkable — asking a suspect their tribal status creates an incentive to lie, and the "apparent violation" standard has no clear meaning in existing search-and-seizure law.
Curious how the Court got there? See the step-by-step legal reasoning →
Why it matters
Tribal police across the country can now stop and search non-tribal drivers on reservation roads without first going through a two-step process to establish the driver's tribal status. This means reservation communities are no longer left with a policing gap when non-tribal members are suspected of crimes — including carrying weapons, driving impaired, or transporting drugs — on roads running through their lands.
What changes now
The Ninth Circuit's order suppressing the drug evidence is undone, and the case goes back to the lower courts for proceedings consistent with the Supreme Court's ruling. Cooley's federal drug and weapons prosecution can now move forward using the evidence the tribal officer collected. More broadly, tribal police departments across the country can rely on this ruling to confirm their stop-and-search authority on reservation roads without needing separate cross-deputization agreements to cover every situation.
What this does not decide
The ruling does not give tribal police unlimited authority over non-tribal members. Tribes still lack criminal jurisdiction over non-members; this decision concerns only temporary detention and search before handoff to federal or state officers. Justice Alito's concurrence further limits the holding to roads primarily patrolled by tribal police, reasonable-suspicion stops, protective searches, and probable-cause detentions.
Concurrences and dissents
Concurrence — Justice Alito
Justice Alito joined the majority opinion but wrote separately to spell out precisely what he understood it to hold and no more: on a reservation road primarily patrolled by tribal police, a tribal officer may stop a non-Indian driver with reasonable suspicion of a state or federal law violation, conduct a search limited to protecting officer safety, and — if probable cause exists — detain the driver only as long as it takes for a non-tribal officer to arrive. He did not want the ruling read more broadly.
How the Court got there
The legal reasoning, step by step
- The Court applied the framework from Montana v. United States (1981), which set a general rule that tribal sovereign powers do not automatically extend to non-tribal members, but recognized two exceptions. The second exception — allowing tribes to exercise authority over non-members when their conduct 'threatens or has some direct effect on the health or welfare of the tribe' — was the key legal test here.
- The Court found that second exception fit the facts of this case 'almost like a glove.' Denying tribal officers the ability to stop and briefly hold any person suspected of a crime on reservation roads would leave tribes unable to respond to non-Indian drunk drivers, weapons carriers, drug traffickers, and other threats operating within their own borders — a clear threat to tribal health and welfare.
- The Court drew on its earlier ruling in Duro v. Reina (1990), which held that tribal officers may detain and transport suspected offenders to proper authorities when criminal prosecution lies outside the tribe. The authority to conduct a search before transport follows naturally from that already-recognized power.
- The Court rejected the Ninth Circuit's two-part test as unworkable on two fronts: requiring an officer to determine tribal status before acting creates an incentive for suspects to lie, and conditioning detention on 'apparent' legal violations introduces a novel, undefined standard into search-and-seizure law — a problem that would arise constantly given that non-Indians make up most of the population on many reservations.
- The Court also rejected the argument that existing federal cross-deputization statutes — laws authorizing the Interior Department to grant tribal officers power to enforce federal law — showed Congress had deliberately filled this space and left no room for inherent tribal authority. Those statutes were both too broad (covering arrest powers) and too narrow (not covering state-law violations), and the Court read them as operating on the assumption that tribal authority already existed.
Doctrinal impact
Cases affected by this decision
Reaffirms Montana v. United States (450 U. S. 544)
The Court applied Montana's second exception to confirm tribal policing power over non-members who threaten tribal welfare.
Distinguishes Strate v. A–1 Contractors (520 U. S. 438)
Strate barred tribal court civil jurisdiction over non-members but expressly reserved the tribal police patrol authority confirmed here.
Reaffirms Duro v. Reina (495 U. S. 676)
Duro's recognition that tribal officers may detain and transport offenders to proper authorities supports the search authority confirmed here.