WASHINGTON — The Supreme Court gave churches and religious schools a new shield against civil rights claims from their employees, ruling Wednesday that the principle of church-state separation bars bias suits from teachers who serve as “ministers” of the faith.

In a unanimous ruling, the high court for the first time held the Constitution includes a “ministerial exception” that protects churches and their schools from undue interference from the government and its courts.

Notre Dame law professor Rick Garnett called the ruling “one of the court’s most important church-state decisions in decades.” It “protects religious liberty by forbidding governments from second-guessing religious communities’ decisions about who should be their teachers, leaders and ministers,” he said.

The court did not define which teachers are “ministers.”