SpaceX, the aerospace company headed by Tesla Inc. TSLA Chief Executive Elon Musk, sued the Justice Department, alleging its discrimination case against the company is unconstitutional. SpaceX filed the suit in the U.S. District Court for the Southern District of Texas on Friday. Attorney General Merrick Garland is one of three Justice Department employees and defendants named in the suit. In late August, the Justice Department sued SpaceX, alleging the company discriminated in its hiring by illegally disqualifying applicants who had refuges or asylum status in the U.S. In Friday’s filing, SpaceX said it had “not engaged…