What the prosecution will show is that he refused to deploy and he refused to obey the orders of his brigade commander. If they do that then Lakin is toast.
As "LITTLE V. BARREME" clearly indicates, an officer is personally liable for obeying unlawful orders.
And what Lakin has to show is that the orders of his brigade commander were unlawful. It doesn't look like he's trying to do that.
Since it's up to the trial judge, not the investigating officer, to evaluate affirmative defense that the orders were not lawful, it's not clear that it could be done at the Art. 32 hearing anyway.