In most cases, no matter what the specifics of the regulations for each branch of military service have to say on the subject of uniform wear by retirees and veterans, the end result is the same. You are expected to wear the uniform appropriately, on the right occasions, and you are expected to NOT promote commercial or political causes while wearing the uniform of the Army, Navy, Air Force, Marine Corps, or Coast Guard
From veteran.com :
I can’t find anything about penalties, so I’m assuming this is about as legally enforceable as the “flag code”.