A federal appeals court on Wednesday allowed President Donald Trump to temporarily remove the head of an independent watchdog agency who was investigating the administration’s mass firing of probationary federal employees.

The U.S. Court of Appeals for the District of Columbia sided with the Trump administration in allowing the immediate removal of Hampton Dellinger as head of the Office of Special Counsel while the court battle continues. Dellinger is likely to appeal to the U.S. Supreme Court.

A federal appeals court on Wednesday allowed President Donald Trump to remove Hampton Dellinger as head of the Office of Special Counsel for now, in one of the most prominent legal challenges over presidential power to fire executive branch officials without cause.