Unfortunately, this brief goes to length to build a wall against the question of us having serious military arms. It harps on "common use at the time" with the view that the 2ndA only covers those items which we would normally have outside military application. (Methinks they're just trying to ward off a huge red herring, but it will be a problem for us later.)
...(Methinks they're just trying to ward off a huge red herring....
I would agree about the red herring issue - I think that they want to avoid even a question from one of the Justices to the effect of "So, would ruling in your favor mean that anyone could walk down to the local Home Depot and buy a Stinger missile, counselor?" (or a tank, F15, suitcase nuke, etc., etc. - take your pick).
However, I don't think that we're going to be too terribly limited on full autos by this ruling. You see, there are already something like 200,000 of them out there, and an existing legal process for transfer. Further, the '86 ban is virtually identical in nature to the DC ban, and if Heller wins his case, so should the person/people who bring a case against the BATFE for failing to register a full auto under the provisions of the '34 NFA.