President Donald Trump is asserting a power to pardon himself that not even Richard Nixon tried to claim before resigning the presidency in 1974, and that the Justice Department has said isn’t constitutional. In a legal opinion issued just four days before Nixon stepped down, the Justice Department’s Office of Legal Counsel concluded that a president can’t pardon himself. “Under the fundamental rule that no one may be a judge in his own case, the president cannot pardon himself,” wrote Mary Lawton, who was then acting assistant attorney general.