Throughout the show Frank & Margaret are always talking about other characters violations of military law while completely ignoring the fact that both of them were guilty of adultery with is a general offense under the Articles of War and the UCMJ. Although adultery was so common that it probably wouldn't be charged.
I'm the episode "House Arrest", Hawkeye is charged with striking a superior officer but his defense should have been that the assault happened after he was assaulted by Frank. Both Frank and Margaret should have been charged, both for assault and conduct unbecoming, for instigating the event.