The U.S. Supreme Court issued a broad, unanimous ruling June 1 reaffirming that tribal police officers have the power to temporarily detain and search non-Native Americans on tribal land if they’re suspected of violating state or federal law.

Indian Country saw the ruling as an affirmation of tribal sovereignty. The case before the court was United States v. Cooley. It involved a 2016 incident on Montana’s Crow Reservation where the defendant – Joshua James Cooley – was arrested after a Crow Police Department officer searched his vehicle and found weapons and methamphetamine. A grand jury later indicted Cooley on drug and gun charges, but submitted a motion to suppress the drug evidence on the basis that the tribal police officer lacked the authority to detain and search him because he is not Native American. Two lower courts had ruled in favor of Cooley’s argument, but the Supreme Court overturned those rulings.

“Rightfully, the Court held that tribal law enforcement have the authority to temporarily detain and search non-Indians traveling on public rights-of-way running through a reservation for suspected violations of state or federal law,” said a statement by the National Congress of American Indians (NCAI) and the Native American Rights Fund (NARF).

NCAI president Fawn Sharp said the 9-0 decision is one “of the strongest affirmations of tribal sovereignty in a generation” and helps keep Native communities secure.

“For too long, non-Native criminals escaped justice from crimes committed on tribal lands, but [the ruling] is monumental in changing that. We applaud this decision and look forward to advocating for our member tribes as they improve safety and security in tribal communities as a result of this new precedent,” Sharp said in the statement.

The Supreme Court relied on the second exception of the 1981 Montana v. United States case which states that tribes have the authority to address “conduct [that] threatens or has some direct effect on . . . the health or welfare of the tribe.” The Supreme Court also reasoned that not recognizing the authority to detain suspected non-Native offenders could pose serious threats to public safety in Indian Country. It noted that several state and lower federal courts have recognized the authority and several previous Supreme Court opinions assumed such authority existed. It also pointed out that such detentions of non-Natives do not subject them to tribal law, but only to applicable state or federal law.