The issue focused on about 5,000 federal court rulings that cut rights to legal medical marijuana in four states: California, Colorado, Oregon and Washington.

U.S. Supreme Court Justice Anthony Kennedy said the fact that those decisions were made by courts with political ties to one of the four states who legalized medical marijuana was "unprecedented."

"It is highly unusual for a justice to take this kind of step," he said.

Some critics said the case could also make it easier for