The judge? Or the Court. My understanding is that the Court is the judge of the facts, not the judge, Depending on the makeup of the Court, I'd think they'd be highly adverse to the judge telling them they were not to be the judge of defense's arguments, and that the accused would not be given every opportunity to present his case. I certainly would, regardless of the case, and senior officers tend to be more "protective" of their prerogatives and responsibilities than your typical civilian juror, way more. I've seen that myself in a very similar military environment (Judge, JAG prosecutor, JAG defense, Court or Panel (of which I was the junior member) just not a full Court Martial, but run pretty much the same.
Per the MCM (and affirmed in New), the lawfulness of an order is a matter of law to be determined by the military judge.
The Court evaluates evidence, the judge determines matters of law. As an example, it's not the Court that makes evidentiary ruling based on law, but the trial judge.
In this particular instance, the MCM makes the lawfulness of an order, not a matter of fact, but a matter of law.