WASHINGTON (AP) — House Speaker Paul Ryan says bump stocks — devices that can effectively turn semi-automatic rifles into fully automated weapons — should be addressed through a regulatory change.

The devices have drawn attention because they were found among the arsenal of the killer in the Las Vegas massacre.

Legislation has been introduced in the House and Senate to ban their use. But Ryan says addressing the issue by regulation instead would be “the smartest, quickest fix.”

He also questioned why the Bureau of Alcohol, Tobacco, Firearms and Explosives approved the use of bump stocks in the first place. That happened under the Obama administration.

Bump stocks can fit onto semi-automatic rifles and allow them to fire much more quickly, mimicking fire from fully automatic weapons — which are illegal.