UCMJ - calling a top officer as a witness

In A Few Good Men, there’s some dialogue to the effect that defense counsel in a court-martial could be subjected to military discipline if he calls a commanding officer as a witness but that testimony doesn’t lead to an acquittal. (Of course, in true Hollywood style, Jack Nicholson’s snarling on cross-examination ends up making all the difference for Tom Cruise’s clients).

Is that an actual rule or DoD policy, written or unwritten? Sounds a bit odd to me, as well as a disincentive for defense counsel to zealously represent a client by going wherever the evidence leads him or her.

I think the problem was the ethicality of the line of questioning effectively accusing Nicholson of committing a crime without any evidence to back it up when Nicholson wasn’t on trial. It didn’t have anything to do with him being a superior/commanding officer.

It’s been awhile since I’ve seen the film, but was the testimony not leading to an acquittal the problem, or the testimony being determined to be not material to the case?

In the movie, Tom Cruise’s character isn’t threatened with military discipline if he calls Nicholson’s character as a witness. He’s told by Kevin Bacon’s character, the guy prosecuting:

And as Tom Cruise’s character puts it when his co-counsel suggests putting Jack Nicholson’s character on the stand:

The problem isn’t putting anybody on the stand. The problem is falsely accusing them of a crime.

I suppose in the military courtroom when the brigadier general is being examined by the captain, the rules of a real courtroom apply? That is, the witness cannot be hostile or refuse to answer questions that will not incriminate themself or order the lower-ranking attorney to desist a certain line of questioning?

Are there any privileges that come from rank when someone of a high rank is on the witness stand?

Yes. As in a civilian courtroom, the judge is God.

The privilege to lose a battle of wits with Tom Cruise.

IIRC, unless the officer is HIS commanding officer, he does not necessarily have to obey they order? An officer cannot wander in from another location and start giving the grunts orders that contradict their standing orders?

Standing order for a military lawyer is “you will defend your client”, I assume?

Yeah, in general military personnel are supposed to take orders only from those in their chain of command (specific rules on exceptions vary, as usual, by location). An admiral is always higher-up than a lieutenant, but may or may not be in his chain of command: must be saluted but not necessarily obeyed.