On Tuesday, the Supreme Court heard oral argument in United States v. Cooley. The case concerns whether tribal police officers may detain or search non-Indians suspected of violating state or federal law on public highways running through reservations, and if so, in what circumstances. Tribal police officers’ authority flows from tribal governments, and so this case is also about the scope of tribal governments’ sovereign powers over non-Indians.

The court has previously held in Oliphant v. Suquamish Indian Tribe that tribal courts do not have criminal jurisdiction over non-Indians, and that tribal criminal law does not apply to them. Instead, non-Indians are subject to state or federal criminal law (depending on the crime and Indian status of the victim) and prosecuted in state or federal courts for any illegal conduct. Nonetheless, tribal law-enforcement agencies remain the local police force on Indian reservations and are usually the first responders, though the Indian status of a suspect and victim — and therefore what law applies, and which court system will eventually prosecute — is often unknown when police arrive on the scene.

Cooley addresses very real-world questions about tribal policing. But it also is controlled by a complex and convoluted series of federal common-law cases that have attempted to define the scope of tribal sovereignty for decades. Tuesday’s argument was divided between precisely these two aspects of Cooley. Half of the justices’ questions were about defining the scope of tribal sovereignty, and the other half were about what is possible, safe or workable for tribal police on the ground — in other words, tribal sovereignty in theory vs. practice.

Cooley’s particular combination of facts and law has the potential to provoke both internal conflicts for individual justices and to create strange bedfellows across the court. Tuesday’s argument revealed a court that seems deeply conflicted on just about every aspect of this case from top to bottom, except possibly the outcome.

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