What actually are the constitutional limits to owning weapons?
We know that weapons ‘in common use at the time’ may not be banned, and from
Heller we know this included handguns. Also from
Heller we know that weapons deemed ‘dangerous and unusual’ may be banned, such as a sawed-off shotgun. Recently the U.S. Seventh Circuit Court of Appeals ruled that the Illinois ban on carrying a weapon in public is also un-Constitutional.
Heller, which I read from the OODC link on page 1, only touches (rather unsatisfactorily, IMO) on the kinds of weapons that may be banned without infringing the Second Amendment. Scalia says there will be time to sort it all out and that we've just gotten started on it, and long delays (centuries and decades) are common in constitutional issues.
However, he does point out that some statutes ban weapons "commonly used by criminals" -- the sawed-off shotgun ban, for instance. Well, that certainly describes assault rifles! The reason we are all discussing the issue is that assault rifles are most often used by mass murderers shooting up school, malls, theaters, and workplaces: this is exactly the problem.
On the other hand, Scalia also points out that military weapons commonly carried by infantry may be protected, thus casting into some doubt the banning of the machine gun in 1939, an obvious military weapon at that time. Well, that certainly also applies to the assault rifle! The whole point of that weapon is that it looks military and that is the whole reason psychotics use it to mow down dozens of their fellow citizens: it's fashionable, it's cool, and they even costume to match the gun: the common "ninja commando" costume worn especially by young male psychotics on shooting sprees. Reading
Heller carefully at that point toward the end of the link, I think Scalia is inviting suits based on particular forms of weaponry that are problematic from public welfare concerns --- weapons particularly useful for mass murder.
I am particularly interested in the grenade issue: CLEARLY grenades are a normal military infantry weapon today, and yet are illegal, and yet of the greatest danger to the public: any crazy could just run down halls throwing grenades in each schoolroom or work area he runs past.
DC law (which is administered by Congress) outlawed all handguns and required that any permitted long gun be disabled, completely nonfunctional at all times, no exceptions for defense. This was struck down. However, it was struck down on the basis of handguns being the
normal American self-defense weapon for many years, not an unusual or especially dangerous weapon. It is plain the Court is willing to hear further challenges to the Second Amendment.