When the offending officer is the Commander-in-Chief, standard procedure breaks down. If the orders come down for Marines et al to march on U.S. soil, the unconstitutional order has gone from the very top to the very bottom. Disobedience can surely lead to Leavenworth as easily as going AWOL.

That being said, don’t obey, don’t quit, don’t go quietly either. If you have sworn an oath to support and defend the constitution against all enemies foreign and domestic, keep that oath above all else.