Cases: It's against the law to wear military dress and insignia if you aren't in the military. Who knew? Not Hamilton!
US v. Hamilton, 4th Cir, 11/9/2012
An honorably discharged disabled serviceman shows up at a veteran's recognition ceremony wearing full military dress (with medals he never earned). The government was not amused. In it's typical authoritarian style, he was politely asked to leave (by means of an arrest for criminal charges).
Mr. Hamilton challenged his convictions on the grounds of the first amendment. The Fourth Circuit affirmed the conviction, stating that there was a compelling state interest to maintain the symbolic value of military insignia and to "ensure that the individuals displaying these honors to the general public are those who actually have receive such honors."
Our government is very forgiving of people who commit fraud on investors, consumers, or the general public. But God save you if you choose to do so while wearing military insignia.
No word yet on whether it's okay to continue to wear "sexy soldier" costumes sold at Halloween.