That wasn't very well put. I should have said that "the burden of proving the order unlawful, falls to the defendant...."
And no, the military judge is neither going to grant discover or entertain even for a moment the assertion that Barack Obama may be ineligible for the office, as Barack Obama didn't order Lakin deployed - SecDef Gates did, or someone subordinate to him.
I know the burden is on Lakin to prove the order is unlawful. It will be interesting to see how far up the chain of command he can go, which might be higher than you think. He should be able to get at least Gates. Depending on what he says, maybe even higher.