By Dorothy Alther, CILS Executive Director

On June 1, 2021, the Supreme Court, in a unanimous decision, issued its ruling in U.S. v. Cooley finding that tribes have inherent authority to stop non-Indians on a right-of-way within the boundaries of an Indian reservation who are suspected of committing a state or federal crime. Once stopped, Tribal police officers, acting with probable cause, have the authority to conduct a limited investigation and if evidence of a crime is discovered, the Tribal officer can detain the non-Indian until he or she can be transferred or transported to the custody of state or federal law enforcement.  To those less familiar with Indian Country this ruling might seem to be so obvious that it was unnecessary for the Supreme Court to have announced it in a unanimous ruling.  However, while tribal authority over non-Indians on Tribal land has long been settled, that authority over non-Indians on non-Tribal lands, such as right-of-way, has been less clearly defined until now.

The Cooley case involved a Crow Tribal police officer who encountered a non-Indian stopped on a state highway within the Crow reservation early one morning.  After questioning the driver, the Tribal officer became suspicious of the driver’s story and explanation of where he been and why he was parked on the highway. After detaining the driver and a child who was in the vehicle, the Tribal officer conducted a search of the vehicle and discovered firearms, drugs, and drug paraphernalia. The driver and child were turned over to a local sheriff deputy and Bureau of Indian Affairs police officer, as was the evidence seized during the Tribal officer’s search.  A federal court dismissed the drug and firearm charges against the driver finding the Tribal officer lacked authority to conduct the search, therefore the evidence obtained during the search was inadmissible.  The case was appealed to the Ninth Circuit Court of Appeals, which upheld the suppression of the evidence ruling that Tribal authority over a non-Indian on non-Tribal lands, such as right-of-way, was limited to the Tribal officer first determining whether the driver is Indian. If the driver is non-Indian, a Tribal officer cannot search the driver’s person or vehicle unless there is “apparent or obvious” evidence that a state or federal crime has been committed.  If no such evidence is present, the Tribal officer must release the driver.

In overruling the Ninth Circuit Court, the Supreme Court applied a test created in the 1981 case of Montana v. United States, which provides two exceptions to the general rule that a tribe lacks jurisdiction over non-Indian on non-tribal lands within the reservation. The first exception is when the non-Indian consents to Tribal jurisdiction. Under the second exception, tribal jurisdiction can be extended to non-Indians on non-tribal lands if the person’s conduct “… threatens or has a direct effect on … the health or welfare of the tribe.”  The Supreme Court found that the Montana two exception fit the current case like a “glove.”

CILS paid close attention to this case due to its close work with Tribal governments, particularly Tribal police departments, and representing the California Tribal Police Chiefs Association (CTPCA).  The Ninth Circuit Court decision in Cooley raised practical and safety concerns for Tribal officers who routinely encounter non-Indians on the many state and county right-of-ways that crisscross California Indian Country. The United States, who prosecuted defendant Cooley, sought Supreme Court review of the Ninth Circuit decision seeking not only reversal but clarification on inherent Tribal authority over non-Indians found on non-Tribal lands within the reservation that have or are committing crimes.

CILS, on behalf of the CTPCA, filed an amicus (friend of the court) brief in partnership with the law firm Jenner & Block LLP in support of the federal government’s effort to overturn the Ninth Circuit Court’s decision.  Our brief focused on the day-to-day practical impacts the Ninth Circuit’s ruling would have on Tribal law enforcement officers and public safety in the tribal communities they are sworn to protect. The Supreme Court took note of our argument that negotiating county MOUs or other cross-deputations agreements are not the “be all” solution to Ninth Circuit Court’s ruling.

The Supreme Court’s decision in Cooley has given Tribes, their Tribal police officers the clarity needed when encountering non-Indians committing crimes on non-Tribal lands within a Tribe’s reservation.  The decision also establishes additional definition on the reach of inherent Tribal authority over non-Indians in general and to the application of the Montana two exception. The Supreme Court decision is clearly a win for Tribes, Tribal law enforcement and to Tribal community safety.

The U.S. v. Cooley decision here

If you have further questions regarding the holding or the impacts of the decision on your tribal law enforcement department please contact Dorothy Alther at or Jedd Parr