WASHINGTON – In a case that may threaten the future of public-employee unions, the U.S. Supreme Court on Monday ruled so-called agency fees charged to certain nonunion members violate those members’ First Amendment rights.

The high court stopped short of barring all public-employee unions from charging agency fees to nonmembers. The employees in the case before the court—Illinois home care workers—were not “full-fledged” public employees, the court said.