The legal question hinges on the Civil Service Reform Act of 1978, which Trump says gives him the authority to remove collective bargaining powers from the unions owing to national security concerns. Unions such as NTEU and the American Federation of Government Employees disagree.

A union that represents 150,000 U.S. government employees filed a lawsuit on Monday seeking to block President Donald Trump from stripping hundreds of thousands of federal workers of the ability to collectively bargain with government agencies through their unions.