The Supreme Court won't step into a dispute between Michigan gaming officials and a group of harness racing drivers over allegations of race-fixing.

The drivers had refused to speak to state investigators without a grant of immunity from prosecution. The 6th U.S. Circuit Court of Appeals ruled last year that they had a constitutional right to remain silent.

Michigan officials argued that gaming officials did not have to grant immunity before taking action against the drivers. The drivers were never charged with any crimes.

The justices on Monday left in place the appeals court ruling. Harness racing is a form of horse racing.