President Donald Trump has expounded an extraordinary vision of his authority over the past month, relying on the Supreme Court’s decision last year granting him immunity from criminal prosecution, as a blank check in his broader drive for power.

The U.S. Supreme Court has allowed presidential power to steadily expand in recent decades. Now the court may review Trump administration efforts to expand executive branch authority.

Donald Trump is already testing his sweeping assertion of presidential power with the US Supreme Court, which just a month into his new term is poised to say whether he can fire the head of a federal whistleblower agency.