WASHINGTON – The Supreme Court says the Labor Department must do a better job of explaining why it is changing a longstanding policy on whether certain workers deserve overtime pay.

The justices on Monday asked a lower court to take another look at whether federal law allows the agency to require overtime pay for people working as service advisers at auto dealerships.

The 6-2 ruling comes in a case involving a California auto dealer that claims its service advisers are similar to car salesmen or mechanics, who are exempt from overtime requirements under the Fair Labor Standards Act.

A federal district court sided with the dealer. But the federal appeals court in San Francisco deferred to a new Labor Department rule stating that service advisers are not exempt from overtime.