When President Trump tweeted that he has the constitutional authority to pardon himself, he likely weakened his case in the minds of most ordinary people. Why would he talk about pardons if he hasn’t done anything for which he might need one? But as a legal and constitutional matter, Trump is not wrong. Presidents do have the constitutional authority to pardon themselves, albeit at the considerable risk of impeachment if they do so.
The president’s pardon power was intentionally made broad, even though the framers of the Constitution were well aware that it could be abused. They understood the pardon as an essential final check against miscarriages of justice and overly harsh applications of the letter of the law — and more importantly, as a device for national reconciliation after episodes of political unrest. George Washington used the power this way after the Whiskey Rebellion, Abraham Lincoln after the Civil War, and Jimmy Carter after Vietnam.
Article II, Section 2 of the Constitution says the president “shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment.” The exception for impeachment shows that the clause extends to presidential misconduct, and suggests the ultimate remedy is impeachment by the House and conviction by the Senate, rather than criminal prosecution.