WASHINGTON • The Trump administration has issued a new rule banning bump stocks, the attachments that enable semi-automatic rifles to fire in sustained, rapid bursts and that a gunman used to massacre 58 people and wound hundreds of others at a Las Vegas concert in October 2017.

The new regulation, which had been expected, would ban the sale or possession of the devices under a new interpretation of existing law.

Americans who own bump stocks would have 90 days to destroy their devices or to turn them in to the Bureau of Alcohol, Tobacco, Firearms and Explosives, or ATF.

The Justice Department said on Tuesday ATF would post destruction instructions on its website.

Bump stocks work by harnessing a firearm's recoil energy to slide it back and forth to bump against a squeezed trigger, so that it keeps firing without any need for the shooter to pull the trigger again.

The Justice Department said that this function transforms semi-automatic weapons, like assault rifles styled on the AR-15, into fully automatic machine guns, which Congress sharply restricted in 1986.

A senior Justice Department official, briefing reporters about the new rule on condition of anonymity, said that it was believed that tens of thousands of bump stock devices are in circulation, but that more exact figures are unavailable. The official said the department expected that most owners of the devices would comply with the new regulation, and that ATF would investigate and take legal action against those who violate it.

Meanwhile, a safety panel set up by US President Donald Trump in the wake of numerous school shootings recommended on Tuesday that schools consider arming staff and using veterans as guards.

The Federal Commission on School Safety panel, led by Education Secretary Betsy DeVos, rejected calls to increase the minimum age required for gun purchases, arguing in its 180-page report that most school shooters obtain their weapons from family members or friends.

Instead, it suggested arming staff - even teachers in some circumstances - "for the sake of effectively and immediately responding to violence".

School districts where police responses could be slower, such as rural districts, may benefit in particular, the commission said. It also recommended that education authorities hire military veterans and former police officers, who "can also serve as highly effective educators".

NYTIMES, AGENCE FRANCE-PRESSE