Is Washington, DC's National Guard unconstitutional?

University of Tennessee law Professor Glenn Reynolds has a piece to day in the NY Post, "Lawyers, Guns & Washington," discussing the legal angles of the upcoming Supreme Court case on the constitutionality of Washington, DC's ban of privately-owned firearms.

Glenn writes there are really just three types of rulings that SCOTUS can decide on:

• One is that the 2d Amendment is a "relic of an older era" that need not apply today, but that, of course, leaves open the question of what other parts of the Bill of Rights can be similarly discarded.
  
• Another is that "the court can find ... that the Second Amendment supports an individual right on the part of law-abiding citizens to possess firearms of the sort that are in ordinary use."

The third option Glenn discusses is this:

It can find that the Second Amendment doesn't grant individual rights, but only protects the right of states to arm their militias (or "state armies," as some gun-control advocates put it). This would make the DC case go away, but at some cost: If states have a constitutional right, as against the federal government, to arm their militias as they see fit, then states that don't like federal gun-control laws could just enroll every law-abiding citizen in the state militia and authorize those citizens to possess machine guns, tanks and other military gear.

But the District of Columbia is not a state, it is a federal district, founded by act of Congress and not even enjoying full representation in the Congress. In fact, for most of America's history, DC had no representation at all nor any political autonomy, being governed more or less directly by the Congress itself.

As UCLA law prof. Eugene Volokh explains, the "states rights" view of the 2d Amendment,

... is probably among the strongest intuitive foundations for he view—after all, “State” appears right there in the text, seemingly referring to each state’s needs and interests. The reading would suggest the right might cover only those whom each state explicitly chose as its defensive force, perhaps a state-selected National Guard. And it would suggest the Amendment doesn’t apply outside states, for instance in the District of Columbia: “‘the District of Columbia is not a state within the meaning of the Second Amendment and therefore the Second Amendment’s reach does not extend to it’” [citing the D.C. Circuit dissent].

But if the 2d Amendment refers solely to the rights of states of the union to have "state armies," as Glenn puts it, and if DC is not a state within the meaning of the Amendment, as the DC Circuit Court's dissent held, then how can the District constitutionally have a National Guard?

I wonder whether this angle will come up before the court.