A presidential self-pardoning power would seriously undermine the rule of law. If presidents could self-pardon, they could engage in monstrously wrongful and criminal conduct with impunity. That would utterly violate the framers’ belief in a limited presidency and in the idea that no president is above the law.
James Madison said, “No man is allowed to be a judge in his own cause.” Self-pardoning presidents would be acting as their own judge and jury, which no one is permitted to do in our constitutional scheme. It would stand in jarring contrast to the rest of the Constitution.
Then there’s the matter of actual precedent. No president has ever decided to pardon himself, including Richard Nixon, George H.W. Bush and Bill Clinton, who all faced special prosecutors investigating their conduct. Self-pardoning would have been seen as a clear-cut admission of guilt, not to mention an outrage against the constitutional order. Further, if the pardons were challenged and invalidated, presidents would have the worst of both worlds — they would be open to prosecution, and their guilt would be widely believed.