Trump cited "numerous legal scholars" in claiming the power to pardon himself, but there does not appear to be consensus on that point. No president has ever attempted it. No court has ever tested it. One historical view is that a president may have the power, but that it wouldn't grant him or her immunity from prosecution after leaving the presidency. In a legal opinion issued during the administration of President Richard Nixon, the Justice Department argued a president could not give himself a pardon because of the longstanding legal principle that no person could be the judge of his own case. Trump has begun a practice of pardoning others: Last week he pardoned conservative commentator Dinesh D'Souza; before that, former Vice President Dick Cheney's adviser Scooter Libby, Maricopa County, Aiz., Sheriff Joe Arpaio and others. Trump also has granted a posthumous pardon to boxing great Jack Johnson, which clemency supporters have said could encourage more prisoners or people who have been convicted to try to get their cases onto his desk.