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.
Because of the de facto officer doctrine, it wont' go any higher than the authority who actually signed the deployment order. That could be Gates, but my guess is that it was probably a two-star. Why is that? Because the de facto officer doctrine makes the eligibility of the issuing officer irrelevant, as a matter of law. This is well-settled military law. This is why Obama is COMPLETELY irrelevant and immaterial to the charges specified. If Lakin had consulted with competent military representation, he could have been advised of such in mere moments.
From NORTON V. SHELBY COUNTY, 118 U. S. 425 (1886)
"The doctrine which gives validity to acts of officers de facto, whatever defects there may be in the legality of their appointment of election, is founded upon considerations of policy and necessity, for the protection of the public and individuals whose interests may be affected thereby.... For the good order and peace of society, their authority is to be respected and obeyed until, in some regular mode prescribed by law, their title is investigated and determined. "
Such application of de facto has been made in a number of military cases including, United States v. Jette, 25 M.J. 16 (C.M.A. 1987) and United States v. Brown, 39 M.J. 114 (C.M.A. 1994)
Keep in mind, the military judge wouldn't even touch this, as I'm presuming (surely safely) that the commander(s) that actually issued Lakin's order, hold their billets without defect.