This matter—the limits of executive power—has deep historical roots. During the period of royal absolutism, English monarchs asserted a right to dispense with parliamentary statutes they disliked. King James II’s use of the prerogative was a key grievance that lead to the Glorious Revolution of 1688. The very first provision of the English Bill of Rights of 1689—the most important precursor to the U.S. Constitution—declared that “the pretended power of suspending of laws, or the execution of laws, by regal authority, without consent of parliament, is illegal.”
To make sure that American presidents could not resurrect a similar prerogative, the Framers of the Constitution made the faithful enforcement of the law a constitutional duty.
The Justice Department’s Office of Legal Counsel, which advises the president on legal and constitutional issues, has repeatedly opined that the president may decline to enforce laws he believes are unconstitutional. But these opinions have always insisted that the president has no authority, as one such memo put it in 1990, to “refuse to enforce a statute he opposes for policy reasons.”