Petitioner’s theory that the President is absolutely immune from criminal prosecution, if accepted, has the potential to severely undermine the Commander-in-Chief’s legal and moral authority to lead the military forces, as it would signal that they but not he must obey the rule of law. Under this theory, the President could, with impunity, direct his national security appointees to, in turn, direct members of the military to execute plainly unlawful orders, placing those in the chain of command in an untenable position and irreparably harming the trust fundamental to civil-military relations….

...the rule of law is critical to the military’s mission and to the people’s trust in the armed forces. The military service members’ duty to disobey unlawful orders plainly illustrates this point. This duty requires service members, who are bound to obey all lawful orders, to disregard patently unlawful orders from their superiors and prohibits service members from using such orders as a defense to criminal prosecution. Immunizing the Commander-in-Chief from criminal prosecution, as Petitioner argues for here, would fly in the face of that duty, creating the likelihood that service members will be placed in the impossible position of having to choose between following their Commander-in-Chief and obeying the laws enacted by Congress… Not only does Petitioner’s approach threaten to inject chaos into military operations, it also threatens to damage—potentially irreparably—the public’s trust in the military and the willingness of recruits to join the armed forces.

….the notion that predicted defiance of the Commander-in-Chief’s orders is the backstop against criminal behavior by a President is not what the Constitution provides for. It would inexorably lead to deep divisions between the armed forces’ political and military leaders and would place servicemen and women in the impossible position of either ignoring presidential orders they are sworn to obey or committing crimes at the President’s behest in violation of their oath—for which they may be prosecuted.