Less than a day after Michael McLendon fired his last shot, gun control groups issued press releases that cited his murderous rampage through three Alabama towns as an argument for reviving the federal "assault weapon" ban. The Obama administration also wants to bring back the ban, on the theory that outlawing the firearms supposedly favored by gangbangers and homicidal maniacs will reduce the casualties they inflict. But there is little reason to believe such laws can deliver on that promise.

Last week, Paul Helmke, president of the Brady Campaign to Prevent Gun Violence, claimed McLendon "needed the firepower of assault weapons to execute his plan of mass carnage." In a joint statement, five anti-gun groups demanded "an effective federal assault weapons ban," calling the Alabama massacre the latest in "a string of preventable tragedies committed with these military-style weapons." They identified McLendon's weapons as "a Bushmaster AR-15-style assault rifle and an SKS assault rifle," which they described as "military-bred firearms developed for the specific purpose of killing human beings quickly and efficiently."

In truth, neither of these guns is an assault rifle, which by definition is capable of firing automatically. Both of McLendon's rifles, like all the guns covered by "assault weapon" bans, were semiautomatic, firing once per trigger pull.

Gun control groups deliberately foster confusion between "assault weapons," an arbitrary category based mainly on appearances, and machine guns, which are already strictly regulated under federal law. The confusion was apparent in news coverage of McLendon's shooting spree, which erroneously called his guns "automatic weapons" and "high-powered assault rifles."

Furthermore, the standard version of the SKS, because it has a fixed magazine, was not covered by the federal "assault weapon" ban. It's not clear from press accounts whether McLendon's Bushmaster rifle would have been covered by the law; the company makes an "post-ban" version of the AR-15 that complies with state laws similar to the federal "assault weapon" ban because it does not have a collapsible stock or a bayonet mount.

As those modifications suggest, the definition of "assault weapons" has little to do with features that make a practical difference in the hands of criminals (who in any event rarely use these guns). The aspect of the federal "assault weapon" law that had the most functional significance was the ban on magazines holding more than 10 rounds. But that provision is unlikely to make a difference in crimes like McLendon's, since magazines can be switched in a few seconds, and the time can be shortened by taping them together (as McLendon did). Not to mention the fact that plenty of pre-ban large-capacity magazines would be available to a determined killer.

In any case, the focus on the specific guns used in attacks like this is misleading because murderers don't need much "firepower" when they're attacking defenseless victims at random. The day after McLendon, using a rifle that anti-gun activists called an "assault weapon," killed 10 people in Alabama, a teenager used a 9mm Beretta pistol to kill 15 people in Germany. The deadliest mass shooting in U.S. history was accomplished with two ordinary handguns; so was the second deadliest.

McLendon carried a .38-caliber handgun and a shotgun in addition to his rifles, at least one of which apparently did not qualify as an "assault weapon." Had he been prevented from buying the Bushmaster, he could have armed himself with any number of hunting rifles that accept detachable magazines. As an agent with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives noted after the murders, "any gun is lethal."

Last year, when the U.S. Supreme Court explicitly recognized for the first time that the Second Amendment protects an individual right to arms, it suggested that prohibiting "dangerous and unusual weapons" nevertheless could be constitutional. That is the loophole supporters of "assault weapon" bans will try to exploit. Their success will depend on the extent to which the courts scrutinize the specious distinction between good and evil guns.