The New York Times explains why the Florida Senate rejected a "two-year moratorium on sales of AR-15 semiautomatic rifles" on Saturday: "The votes just aren't there." While that is tautologically true whenever a bill fails to gain majority support, the point in this case is that the votes really should be there, given that 62 percent of Florida voters "favored an assault weapons ban" in a recent poll. The implication is that Republican legislators, blinded by ideology and fear of the NRA, are defying the will of the people.

That is one possible explanation. Alternatively, it could be that Republican legislators oppose an "assault weapon" ban because they think it is not worth supporting. The latter interpretation gains credibility when you notice that supporters of such legislation, rather than offering a logical argument in its favor, tend to treat it as self-evidently dictated by "common sense." When they try to do more that, the best they can offer is misdirection and obfuscation.

Last week, for instance, an article in the Times said AR-15-style rifles are particularly deadly because they are "fed with box magazines" that "can be swapped out quickly, allowing a gunman to fire more than a hundred rounds in minutes." But that is true of any gun that accepts detachable magazines, including many models that do not qualify as "assault weapons."

Yesterday the Times reported that "military-style rifles" fire "lightweight, high-speed bullets that can cause grievous bone and soft tissue wounds," injuries worse than those typically caused by handguns. As one trauma surgeon explains, "the energy imparted to a human body by a high-velocity weapon is exponentially greater" than the energy imparted by a handgun. But that observation is true of rifles in general; it is not unique to so-called assault weapons.

While the .223-caliber round typically fired by AR-15-style rifles does have a relatively high muzzle velocity, other cartridges, fired by guns that are not considered "assault weapons," equal or surpass it. Furthermore, muzzle velocity is not the only factor in a bullet's lethality; size also matters, and so-called assault weapons fire smaller rounds than many hunting rifles. Both velocity and mass figure into muzzle energy, a measure of a bullet's destructive power. As UCLA law professor Eugene Volokh notes, "the .223 rifles that are often labeled 'assault weapons' have a much lower muzzle energy than familiar hunting rifles such as the .30-06."

More to the point, neither muzzle velocity nor muzzle energy has anything to do with the definition of "assault weapons," which hinges on military-style features such as folding stocks, pistol grips, and barrel shrouds. And while all so-called assault weapons accept detachable magazines, many guns that accept detachabale magazines do not fall into this arbitrary category because they lack the features that offend politicians like Sen. Dianne Feinstein (D-Calif.), who sponsored the federal "assault weapon" ban that expired in 2004 and has been pushing a revised version since the mass shooting in Parkland, Florida, last month.

To give you a sense of how silly Feinstein's distinctions are, her bill specifically exempts the Iver Johnson M–1 Carbine (above right, top) and the Ruger Mini-14 (above right, bottom), but only when they have fixed stocks. Adding a folding or adjustable stock to these rifles transforms them from legitimate firearms into proscribed "assault weapons," even though that change does not make them any more lethal or suitable for mass murder. That's the sort of nonsensical line drawing that must be defended by any honest and well-informed advocate of a renewed "assault weapon" ban, assuming such a person exists.