"After all, it concluded that Miller's possession of a sawed off shotgun could be regulated because it wasn't in 'current military use'."
The above wasn't exactly the holding in the Miller case. The Supreme Court held that:
"In the absence of any evidence tending to show that possession or use of a 'shotgun having a barrel of less than eighteen inches in length' at this time has some reasonable relationship to the preservation or efficiency of a well regulated militia, we cannot say that the Second Amendment guarantees the right to keep and bear such an instrument."
By the way, short barreled shotguns (and rifles) are, and have been, used for military purposes. The court did not explicitly rule that short-barreled shotguns were not covered (this is where Miller is widely misunderstood). The Court only held that they were unable to make that determination (basically punting the issue back to the lower court to consider the question). Unfortunately, those proceedings never happened.
Regardless, here is an interesting thought:
Miller would be highly useful as precedent if a State sued the Federal government over the constitutionality of Federal gun control laws (yes I am dreaming). So far all (to my knowledge) jurisprudence regarding the Second Amendment has concerned private citizens (as Defendants or Plaintiffs), but a State suing the Federal government (as a Plaintiff) would be a whole different matter that negates ALL the anti-gunners current legal arguments.
There is no reason why (other than lack of political will) that a State could not sue the Federal Government to overturn the National Firearms Act (NFA). For example, the Montana legislature could pass a law mandating that every household, in which an eligible able-bodied male between the ages of 17 and 45 resided, have in its possession an M-16 (currently restricted by the NFA). This would obviously have the civic purpose of enabling Montana's Governor to call up private Citizens (who are properly armed) for militia duty, at a moments notice in the event of a dire emergency.
It would only take one freedom-loving State with a like-minded governor, legislature and attorney general to bring the whole Federal gun control system crashing down. Right now no State has the political will to assert its rights, but that may change. I used Montana as an example since they are pushing a similar envelope right now with their Firearms Freedom Act legislation (currently being litigated in the Federal Courts), let's hope the trend continues.
The current crop of Second Amendment cases being litigated by Pro-Rights groups (such as the Second Amendment Foundation, i.e. Alan Gura) are looking to settle the scope and meaning of the Second Amendment from an individual civil rights legal perspective. While this is wise and prudent, at some distant future point in time, this legal line of reasoning will have run its course. Having a State take up the matter of the 2nd Amendment (as a bulwark against Federal encroachment of State powers) is no different than a State suing to keep the Federal government in check on 9th and 10th Amendment grounds. All three of these areas remain virtually unexplored via legal channels.