It seems to me that whenever we have a high-profile shooting in America, talk of renewing the ban on "assault weapons" is among the first responses. This makes sense, because "assault weapon" is a provocative term that currently has no less-provocative term (in part because it describes a largely nonsensical grouping of weapons). It's hard to sound rational defending "assault weapons," and there's no good alternative term to use.
But I certainly do defend the use of "assault weapons." Back to the 2009 report - 5% of the criminal weapons examined were assault weapons; 75% were handguns. This is an obvious, intuitive result. Assault weapons are not easily concealable but are good for winning gunfights; handguns are much more easily concealable and are fairly bad at winning gunfights. Legitimate personal defense scenarios are gunfights almost by definition, whereas a gunfight is obviously anathema to a gun crime gone well. Why worry about "assault weapons" (which I think I might start calling "home defense weapons") and not guns that are not only suited to crime but actually used in crime?
I don't mean to imply that the handgun is a "criminal's weapon." I only mean to state the self-evident fact that if one is planning to commit a crime with a gun, a handgun is most likely to be the gun best suited to the crime.
We should take a moment here to address the question of why handguns are not often used in mass shootings. I don't know if any studies have been done on this subject, but I think the truth is that the weapon used doesn't matter much. As I understand it, mass shootings tend to occur at close range and the victims tend to be unarmed. In that sort of scenario, any gun will allow the shooter to kill a large number of people in a short amount of time. Sandy Hook involved magazines that can hold 30 rounds, which is a lot for a rifle. Banning high-capacity magazines (as California does) in response seems quixotic. Ejecting an empty magazine and loading a fresh one is a matter of seconds - a long time in a gunfight, but a very short time in a massacre. The relevant question in a mass-shooting scenario is not how many rounds the shooter's weapon holds, but how many rounds the shooter has brought with him. It is only when somebody starts shooting back that having a high-capacity magazine is a material advantage.
So back to gun control. Discussion of gun policy, and gun philosophy, in America always seems to come back to the Second Amendment, so I'll start with some thoughts on that. As I've already said, I think the Second Amendment was inspired by an assumption that was demonstrably wrong even in the late 18th century. The notion that an armed populace is a free populace is simply wrong, and always has been. However, being predicated on a false premise does not make the Second Amendment any less the will of the people.
What frustrates me most about the Second Amendment is how people on both sides of the "gun control debate" seem to twist it. Can there be any serious doubt that the Framers intended the Second Amendment to promote a thriving militia system (however wrong they may have been about the utility of such a system)?
If that be so (and I think it is), I do not see how the Second Amendment can be seen to guarantee the right to keep arms in the home. As Posner has correctly pointed out, a rational militia commander might well want his troops to keep their weapons in a central location (such as the muster point), so when the militia is called out there is no risk that somebody shows up without their gun (or some other essential military kit). That is, in fact, how many 18th century militia operated - Concord and Lexington wouldn't have happened otherwise. And certainly a thriving militia system (which I don't think we have) doesn't imply the right to keep a gun in a "functional" state, as Heller held. Even if the militia is going to be called out to resist a court judgment (as it sometimes was), there is time to assemble one's weapon.
At the same time, a thriving militia system does imply the right to own weapons of the sort in common use by the militaries of the day. The modern notion that peaceable citizens have no business owning automatic weapons is thoroughly anti-militia. A modern militia's armory should look like the National Guard's (which I don't think is a militia, although it is so designated by United States law) - only owned by private citizens.
To put this in perspective, I think the Second Amendment guarantees the right to privately own a main battle tank, but not the right to keep even a single-shot pistol in one's home, let alone loaded. I don't think either side of the gun control debate would be happy with that outcome, but I think that's what the amendment says. This is why I think the Second Amendment is largely superfluous when discussing questions of weaponry, even in the United States - it's a cultural touchstone, but it addresses an entirely different question than occupies current gun politics.
So, leaving the Second Amendment aside, here are two few features of gun control laws that I'd like to see that are not, to my knowledge, common:
1. A positive correlation between how heavily regulated a weapon is and how suited it is to most crimes. The current American approach is to regulate a weapon based on its potential for mass carnage. This seems ... not so much bad, as just silly. To be sure, a heavy machine gun can kill more people in a shorter period of time than can a snub-nosed revolver. The machine gun also weighs well over 100 pounds and is almost five and a half feet long. It has features that make it inherently difficult to commit crimes with. The revolver, while far less able as a weapon, has features that make it much more attractive than the machine gun as a weapon of crime. It isn't so much that regulation of the machine gun is bad so much as the relative lack of regulation of the handgun is absurd. We have a lot of data on what kinds of guns are actually used to commit crimes, and our gun regulation doesn't seem to be aware of it.
2. A shift in focus from the right to own to the ability to use. American gun control laws currently seem to focus on making sure that only the right sort of people can buy guns - people who are not felons, not mentally ill in the psychiatric sense, and so forth. That by itself doesn't seem bad to me, but the truth is, even a paragon of civic virtue is the wrong sort of person to own a gun if he doesn't train holistically in its use. It seems absurd to me that one can own a gun without demonstrating at least a modicum of proficiency in its use; the truth is it seems absurd to me that one can own a gun without demonstrating proficiency in all things firearm-related on a regular basis. I don't mean to trot out the old "anybody can buy a gun but you need to pass a test to drive a car;" I think cars are much more dangerous than guns (about four times as many automobile deaths as gun deaths in the U.S., despite the fact that we have more civilian-owned guns in the US than passenger vehicles). To me, the only point that needs to be made is that a gun is a weapon, and nobody should own a weapon of any kind without facility in the operation and philosophy of that weapon. We don't legislate philosophy in America, but I think it's ridiculous that we don't even require facility with operation.
That second point is a subset of what I think is the biggest problem with America's gun culture in general: even those who don't own guns are prone to think of them in terms of personal empowerment. I don't think that's the way weapons work. To be honest, I don't even think that weapons are simply tools, a "pro-weapon" view I sometimes hear articulated. I own a shovel, but I do not feel like a bad person because I do not regularly practice shoveling (despite the fact that I am actually fairly bad at shoveling). Weapons are not like that. I don't own a weapon because I do not currently have the income (and previously didn't care to make the time) to regularly practice weaponcraft. A weapon is not just a tool. It's a challenge.