IN THE aftermath of the deadliest U.S. mass shooting in modern history, the National Rifle Association signaled it was open to restrictions on the kind of devices the Las Vegas gunman attached to legal semiautomatic weapons to create the rapid fire that killed 58 people. Could it be, finally, that the group was willing to accept some minimum protections against gun violence? Alas, no. The NRA comments were nothing more than a gambit and, sad to say, it looks as if Congress is once again falling into line.

The use of bump stocks — which allow legal semiautomatic weapons to fire like machine guns — in the Oct. 1 shooting created momentum for a ban on the devices. Sen. Dianne Feinstein (D-Calif.) revived her push for legislation, House Speaker Paul D. Ryan (R-Wis.) and House Judiciary Committee Chairman Bob Goodlatte (R-Va.) said lawmakers would take up the issue, and the NRA issued a statement that "devices designed to allow semiautomatic rifles to function like fully automatic rifles should be subject to additional regulations."

Once the horror of those killed and wounded in Las Vegas receded slightly from the headlines, however, the NRA announced its opposition to legislation that would ban the production and sale of bump stocks. Better, the group said, that the Bureau of Alcohol, Tobacco, Firearms and Explosives "review bump-fire stocks to ensure they comply with federal law." And it didn't take long for Mr. Ryan to get the message, backing away from legislation supported by 20 House members from both parties in favor of a supposed regulatory fix. Mr. Ryan wondered aloud how a loophole for bump stocks "happened in the first place."

The suggestion that the ATF is somehow at fault is rather mind-boggling. Congress has tied the agency's hands with laws that give deference to the gun industry, and it is always quick to pounce on the agency when the gun lobby complains about an overstepping of authority. In a letter to Congress, the ATF Association of current and former agency employees explained how the law prohibits the ATF from regulating bump stocks and detailed how the devices were "engineered to avoid regulation under federal law."

Punting the issue to the ATF sets up a catch-22 that ensures no meaningful action will be taken — which is probably what the NRA cynically envisioned. Even if the ATF were to reverse its findings and try to reclassify bump stocks, the likely result would be lawsuits from the manufacturers of these devices, no doubt supported by the NRA.

There is no magic solution to curbing violence, but banning bump stocks would be, as Ms. Feinstein argues, one small, obvious step. Lawmakers seemed to realize that 26 days ago when a gunman used these devices to fire nine rounds per second — 540 rounds per minute — to slaughter and wound people gathered to hear country music. Now the question is: Will they take needed action or, even on this, do the craven bidding of the NRA?