This is one of my all-time favorite movies. But they got a lot of the law wrong.
  1. When Kaffee negotiates with the prosecutor to drop a charge from a "B misdemeanor" to a "C misdemeanor."
    There are no misdemeanors or felonies in military law. There are "offenses" and "serious offenses."
  2. "Aunt Ginny" could not have authorized Jo to speak with Downey; only Downey could do that.
    It's not like he's unconscious and she's his only remaining relative and has to give you medical consent or something. He's an adult and a member of the military; aunt Ginny's got nothing to do with it.
  3. When Ross tells Kaffe that if he accuses Kendrick or Jessep of a crime without proper evidence he would be subject to court-martial for professional misconduct (and the follow-on fretting about it).
    There's nothing in military law that says a lawyer cannot accuse someone else of a crime if it is in his clients' interest to do so. He can ask any question he wants, even if he doesn't have "proof," so long as he has a "good faith basis" for asking the question.
  4. There is no such offense in military law as "conduct unbecoming a marine."
    Conduct unbecoming an officer and a gentleman is an offense, but these two guys were enlisted. In real life they would've been charged with conduct prejudicial to good order and discipline in the Armed Forces (and orders violations, and probably adultery, because they would've investigated these guys and uncovered every bad thing they ever did).