The US Supreme Court has overturned a federal law banning the upgrading of semi-automatic firearms with rapid-fire pistons. The judges ruled on Friday by a vote of six to three that the law passed under then-President Donald Trump violated the Constitution.

In the wake of a massacre in Las Vegas in 2017, it was decided that owners must hand over or destroy the so-called bump stocks. Rapid-fire stocks allow a shooter to fire a massive volley of shots with a single finger press. Fully automatic weapons are prohibited for private ownership in the USA.

The attachments were banned in 2018 because they de facto turn semi-automatic weapons into machine guns. This is not the case, explained Judge Clarence Thomas on behalf of the conservative majority in the Supreme Court created by Trump. A Texas-based arms dealer had filed the lawsuit. The lobby organization National Rifle Association (NRA) welcomed the Supreme Court’s decision.

Liberal Justice Sonia Sotomayor said she would stick with the machine gun definition of the so-called bump stocks: “If I see a bird that waddle like a duck, swims like a duck, and quacks like a duck, I call that bird a duck.”

The campaign team of US President Joe Biden said that the Supreme Court’s decision puts the gun lobby above “the safety of our children”. The leader of the Democratic minority in the House of Representatives, Hakeem Jeffries, called the ruling “dangerous, disastrous and deeply disturbing”. The campaign team of Republican former President Donald Trump, who wants to present himself in the presidential election as a supporter of lax gun laws, said of the ruling that it should “be respected”.

In the Las Vegas massacre in October 2017, 64-year-old Stephen Paddock shot at visitors to an open-air concert from a hotel. He used rapid-fire pistons on most of his 22 weapons and was able to fire more than 1,100 shots in total – up to nine per second. He killed 58 people and injured around 500 others. He then shot himself.

The massacre, like the attack at a high school in Parkland in 2018 that left 17 people dead, sparked heated debates about US gun laws and led to the federal law on rapid-fire pistols. Meanwhile, demolition of the crime scene at the Parkland school in the US state of Florida began on Friday.