WASHINGTON (AP) - The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives could reconsider the lawfulness of "bump stock" devices like the ones used by the Las Vegas gunman only if Congress amends existing gun laws or passes new legislation banning the accessories that allow semi-automatic rifles to mimic machine guns.
The agency, in describing its processes generally on Friday, indicated that Congress, already preparing for next year's mid-term elections, will be responsible for decisions about regulating or banning the devices. The National Rifle Association and some lawmakers had been encouraging the firearms agency to re-examine its judgment in 2010 that the devices were legal and not regulated under U.S. firearms laws. Such a move could have removed some of the political liabilities involved with asking lawmakers to impose new gun controls.
But neither the design of the bump stock nor gun laws have changed since ATF issued its original finding, making it legally problematic and politically untenable for the agency to reverse course.
And it was not immediately clear whether President Donald Trump or Attorney General Jeff Sessions, who oversees the firearms agency, could order it to re-evaluate its 2010 judgment about bump stock devices.
The accessories fit over the stock and grip of a semi-automatic rifle and allow the weapon to fire continuously, some 400 to 800 rounds in a single minute. Bump stocks were found among the gunman's weapons and explain why victims in Las Vegas heard what sounded like automatic-weapons fire as the shooter rained bullets from a casino high-rise, slaughtering 58 people in a concert below and wounding hundreds more.
Sudden endorsements of controls came almost simultaneously from the NRA and the White House.
The NRA, which famously opposes virtually any hint of new restrictions called on ATF "to immediately review whether these devices comply with federal law. The NRA believes that devices designed to allow semi-automatic rifles to function like fully automatic rifles should be subject to additional regulations."
Moments after, at the White House, press secretary Sarah Huckabee Sanders praised the announcement. House Speaker Paul Ryan added his support, as have other top Republicans.
But even with the unusual concession, it is extremely rare that the ATF would reconsider its previous evaluations unless federal law changes. That could be seen as an admission that its earlier evaluation was legally flawed.
The ATF provides the guidance when a manufacturer asks the agency to evaluate a firearm or accessory to determine if it can be sold or if its sale is restricted by either the Gun Control Act or the National Firearms Act.
Changes to existing law or new laws can prompt the agency to reclassify an item, as can alterations to the device or weapon.
The ATF stressed that its classification is specific to each item submitted. And it is based on the most current laws on the books at the time, as well as on a physical examination of the item.
The nation's largest gun lobby and most Republicans have stood firmly in recent years against stricter gun regulations, even as one mass shooting after another horrified the nation. Even gunfire that left House Majority Whip Steve Scalise near death at a baseball practice earlier this year didn't change the equation.
But this time, the deadliest mass shooting in modern U.S. history, combined with the opportunity to back a limited change that could potentially be accomplished administratively, spurred a shift.
The device, which retails for around $200, is not known among gun dealers as an item that is hugely popular. It causes the gun to buck back and forth, repeatedly "bumping" the trigger against the shooter's finger. Technically, that means the finger is pulling the trigger for each round fired, keeping the weapon a legal semi-automatic. Because it creates a significant rocking motion it also means that the gun is "spraying" bullets and it's difficult to hit a target.
Associated Press writers Lisa Marie Pane in Atlanta and Sadie Gurman in Washington contributed to this report.