Your post is all in italics, but I think I understand the question. Miller was ~'34? the Scotus since about that time has taken over fed court rulemaking and Constitutional issues can;t be brought up. Whether, or not he was officially a State militia member could though. Maybe at one time this org got a certificate (ceremonial) from a governor of AK, that said congrats xxx militia for a great job, or something. In order to be a regular State Militia, they'd need much more than that. Like orders from the Gov. The trial court must make the State Militia determinaiton.
Of course they can, but not before the jury. Under those federal rules, the judge determines what the law is, including if it's a law at all, while the jury determines the facts of the case. That is, did the defendant violate the "law", not "what is the law, is it valid or not?".