Narrow though it was, the California Supreme Court on Monday carved out an exception to one of its seminal arbitration rulings, provoking a fair amount of sniping between the majority and the dissent.

By a 4-3 vote, the court held that arbitration awards can be vacated if employees under mandatory arbitration agreements are deprived through legal error of hearings over unwaivable statutory rights, such as those provided by the state’s Fair Employment and Housing Act.