"Few provisions in the U.S. Constitution grant the President an authority as free from legislative constraint as the Pardon Clause. It vests the President 'plenary' power to grant 'Reprieves and Pardons' for 'offences against the United States.' Plainly put, the President can 'forgive' those facing criminal liability under federal law. While the pardon power has been wielded in numerous instances throughout American history, there is limited case law interpreting it. This lack of judicial guidance, coupled with relatively limited discussion of the pardon power at the Constitutional Convention in Philadelphia, has beget various unsettled legal questions concerning the pardon power's scope and breadth. For instance, whether the President may issue a self-pardon has been the subject of conflicting views and debate."
CRS Legal Sidebar, LSB10186