At a press conference today, President Obama said the gun control task force headed by Vice President Biden has given him "a list of sensible, common-sense steps that can be taken to make sure that the kinds of violence we saw at Newtown doesn't [sic] happen again." Sensible and common-sense! Who could be against that? Still, note that Obama, who a month ago conceded that "no single law [and] no set of laws can eliminate evil from the world or prevent every senseless act of violence," is now promising just that. He reiterated that unrealistic goal later in the press conference, saying he wants "sensible steps that we can take to make sure that somebody like the individual in Newtown can't walk into a school and gun down a bunch of children in a shockingly rapid fashion."

So when Obama unveils his specific proposals later this week (as he said he would do), it will be fair to ask: Would these measures have stopped Adam Lanza from murdering 26 people at Sandy Hook Elementary School? Can they reasonably be expected to prevent such horrifying (but rare) crimes in the future? Regarding the three major changes Obama already has endorsed (which he endorsed again at the press conference), the answer to both questions is clearly no:

1. If the federal "assault weapon" ban that expired in 2004 had still been in effect, it would not have stopped Lanza, because the rifle he used was not covered by that law (or by Connecticut's ban, which uses similar criteria). More to the point, such laws hinge on features that have little or nothing to do with a gun's killing capacity in the hands of a mass murderer (or an ordinary criminal). That would still be the case under a California-style law or under whatever definition Sen. Dianne Feinstein (D-Calif.) proposes in her new bill. "Assault weapon" bans leave killers with plenty of equally deadly alternatives.

2. Better background checks would not have stopped Lanza, who used guns legally purchased by his mother and in any event does not seem to have had a disqualifying psychiatric or criminal record. The latter is true of most mass murderers.

3. A limit on magazine size would do nothing about the many millions of "large capacity ammunition feeding devices" already in circulation, even if we assume that the seconds it takes to switch magazines make an important difference in assaults on defenseless moviegoers or schoolchildren.

Yet Obama insisted today that "my starting point is to focus on what makes sense, what works." Works in what sense?