WASHINGTON (AP) — The Supreme Court ruled Thursday that a large chunk of eastern Oklahoma remains an American Indian reservation, a decision that state and federal officials have warned could throw Oklahoma into chaos.

The court's 5-4 decision, written by Justice Neil Gorsuch, means that Oklahoma prosecutors lack the authority to pursue criminal cases against American Indian defendants in parts of Oklahoma that include most of Tulsa, the state's second-largest city.

"On the far end of the Trail of Tears was a promise. Forced to leave their ancestral lands in Georgia and Alabama, the Creek Nati...