Will Lakin have to show his BC to get into prison?
No, but he had to show it to enter the military, which is ironic because the Pretender-in-Chief didn’t.
I don't think citizenship is a requirement for a stretch at Leavenworth.
You just hit on something. Lakin should announce that he’s not a citizen and therefore was ineligible to join in the first place thus the Army court has no jurisdiction. And all he has to do is refuse to allow his BC to be released.