WASHINGTON — House Speaker Paul Ryan said regulations are the “smartest, quickest fix" to address rapid-fire devices like the one used in the Las Vegas mass murder.

But he did not address whether he is open to Congress taking legislative action on the issue.

Ryan, of Wisconsin, said he wants to know why the Bureau of Alcohol, Tobacco, Firearms and Explosives allowed the sale of bump-stock devices, which increase the rate of firepower of semiautomatic weapons to mimic fully automatic weapons.

“We think the regulatory fix is the smartest quickest fix and I’d frankly like to know how it happened in the first place,” Ryan said.

Congress banned the sale and manufacture of new machine guns for civilian use in 1986, and machine guns in circulation before then are tightly regulated, limited in number and expensive.

But the ATF issued a series of opinions on bump-fire devices — determining in most cases they were legal — over the past decade. In 2010, the ATF concluded that a bump-stock device submitted by Slide Fire was a firearm part with no automatic function, and therefore not regulated as a firearm under gun laws.

Democratic Sen. Dianne Feinstein of California, who first proposed legislation to ban bump stocks in 2013, said in response to Ryan's statement that the ATF lacks authority under the law to ban bump-fire stocks. Legislation she introduced with fellow Democrats after the Las Vegas shooting would ban bump stocks, trigger cranks and similar accessories that accelerate a semi-automatic rifle’s rate of fire.

"The agency made this crystal clear in a 2013 letter to Congress, writing that ‘stocks of this type are not subject to the provisions of federal firearms statutes,'" Feinstein said in a statement. "Legislation is the only answer and Congress shouldn’t attempt to pass the buck.”

Last week, when MSNBC’s Hugh Hewitt asked Ryan if he was “open to a vote” on bump stocks, Ryan responded, “Yeah, look, I didn’t even know what they were until this week and I’m an avid sportsman.”

“Clearly, that’s something that we need to look into,” he later added.

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