A divided Supreme Court ruled Tuesday that Michigan can't block the opening of an off-reservation American Indian casino because the state's legal challenge is barred by tribal sovereign immunity.

In a 5-4 decision, the high court said the state could not shutter the Bay Mills Indian Community's casino about 90 miles south of its Upper Peninsula reservation.

The ruling was a win for Indian tribes, which have increasingly looked to casinos as a source of revenue and have relied on immunity to shield them from government interference. But it's a disappointment for Michigan and more than a dozen others states that say the decision will interfere with their ability to crack down on unauthorized tribal casinos.

Michigan argued that the Bay Mills tribe opened the casino in 2010 without permission from the U.S. government and in violation of a state compact. The tribe had purchased land for the casino with earnings from a settlement with the federal government over allegations that it had not been adequately compensated for land ceded in 1800s treaties.

Writing for the majority, Justice Elena Kagan said that the federal Indian Gaming Regulatory Act only allows a state to bring lawsuits challenging casinos operating on Indian lands. But the Bay Mills casino was opened outside the tribe's reservation, Kagan said, placing it outside the law's coverage.

Since the casino does not fall under federal gaming laws, Kagan said it is subject to the ordinary tribal immunity that extends to off-reservation commercial activities. Kagan said it doesn't matter that the casino was authorized, licensed and operated from the tribe's reservation.