Washington DC – The Justice Department (DOJ) proposed a new rule on Monday to more closely regulate pistols with "stabilizing braces" allowing them to be fired from the shoulder, which have reportedly been used in at least two mass shootings in the past three years.

Companies now sell accessories that make it easy for people to convert pistols into more dangerous weapons known as short-barreled rifles, which have heightened regulations because they are easy to conceal, can cause great damage, and are more likely to be used to commit crimes, the DOJ said.

Those accessories mean owners can get a short-barreled rifle without going through the National Firearms Act’s background check and registration requirements. Congress passed the law in 1934 to regulate certain "gangster"-type weapons by taxing them, the DOJ explained.

The Gun Control Act of 1968 also puts restrictions on the transport and sale of rifles and shotguns with barrels shorter than 16 inches. Such a stabilizing brace was used by a mass shooter who killed nine and wounded 14 in Dayton, Ohio, in 2019, and a mass shooter in Boulder, Colorado, who killed 10 at a grocery store in March, the DOJ said.

Donald Trump Trump indictment in the balance as Supreme Court prepares to hear challenge to January 6 charges

The shooters in both instances reportedly put the "brace" to their shoulder as a stock. Manufacturers have sold 3 million stabilizing braces since 2013, the proposed rule states.

The department also published model legislation to help states enact "extreme risk protection order" laws, aka "red flag" laws, permitting courts to intervene with those deemed dangerous to keep them away from guns to head off potential mass murders.

Congress has had hearings and proposed legislation – but never sent any bills to the president – to establish a grant program encouraging states to enact laws that allow courts to take firearms away from people suspected of being a danger to the public.