A pair of recent court rulings are giving unions new and potentially potent ammunition against furloughs of public employees.

On Aug. 18, a federal judge struck down a furlough plan in Prince George’s County, Md., holding that the plan violated the U.S. Constitution by unilaterally cutting wages guaranteed through collective bargaining. On July 29, a state judge in Hawaii issued a similar ruling, saying a furlough violated the state constitution and criticizing officials for ordering unpaid leave without first negotiating with public employee unions.