Well he was "promoted" to SGT during his "POW" time and his back pay and any allowances to which he is entitled to, should at the rank(s) from the time he left his "post" until the date of his Court Martial sentence. His reduction to the rank of PVT E 1 is not effective until the "Court" affirms his sentence. They can't reduce him in rank retroactive to the day he "left" his post. So this Congressman should keep his MOUTH SHUT, and work on legislation if he feels this should happen.
Can't punish someone EX POST FACTO remember the US Constitution states this for a FACT. I speak from experience as a former Classification Officer (USMC) assigned to the US Disciplinary Barracks 1974 to 1976 (yes when the OLD BUILDING WE CALLED THE CASTLE still stood. Not to please to see how they are now handling military prisoners.