And even if a President sends troops, he still has to have it pass a vote in congress to continue. That is the brake supplied by the constitution ... if it is a just use of American troops, then the public, through congress will sustain the action, if not, congress can then recall the troops.
All that is 'out the window' in regards to the USMC, who take oath with the President of the United States, not to the constitution as the Army, Air Force, Navy and Coast Guard. Even now, me and the ex have been out of service since early 1980's but when he has a problem with getting records, he still has the option of "Request Mast" all the way to the President and he will be heard.
So far, Inhofe is providing the needed leverage, but an earlier issue resulted in a personal letter from the Commondant of the USMC, a letter from the Office of the Secretary of the Navy, and got St. Louis off their butts and the documents received.
Now, there are still ways around congressional support, such as the NATO action Clinton had to resort to during the Serbian issue. Not only were American troops the main force there, our 'consultants' were there also.