In a ideologically-aligned decision, the U.S. Supreme Court on Friday has struck down a federal ban on bump stocks.

The 6-3 conservative decision invalidated a federal ban supported by then President Trump  on bump stocks, which allows a shooter to convert a semi-automatic rifle into a weapon that can fire at a rate of hundreds of rounds a minute.

“A bump stock does not convert a semiautomatic rifle into a machinegun any more than a shooter with a lightning-fast trigger finger does,” Thomas wrote in his opinion. “Even with a bump stock, a semiautomatic rifle will fire only one shot for every ‘function of the trigger.’”

The ban was implemented following the 2017 Las Vegas mass shooting – the deadliest in U.S. history. The shooter had used guns equipped with a bump stock to kill 60 people and wound hundreds of others.

Under the bad, such devices were classified as a criminal offense by having the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) consider them machine guns under long-standing federal law.

At issue, was a gun control law enacted by Congress in the 1930s in an attempt to target gangsters like Al Capone, who were using machine guns to commit violent crimes.

The law, which required owners to register those weapons, was amended several times and, by 1986, it prohibited Americans from transferring or possessing a machine gun altogether in most circumstances.

Importantly, the amended law defined “machine gun” as a weapon that fires more than one round with “a single function of the trigger,” a phrase that not been precisely defined.

“When I see a bird that walks like a duck, swims like a duck, and quacks like a duck, I call that bird a duck,” Justice Sonia Sotomayor wrote in her dissent. “A bump-stock-equipped semiautomatic rifle fires ‘automatically more than one shot, without manual reloading, by a single function of the trigger.’ Because I, like Congress, call that a machinegun, I respectfully dissent.”

The decision was denounced by New Jersey state Attorney General Matt Platkin, who noted that bump stocks remain illegal under New Jersey law.

“As the state’s chief law enforcement officer, I condemn today’s Supreme Court’s decision holding that bump stocks, which convert semiautomatic rifles into machine guns, are not federally regulated,” Platkin said.

“To be clear, bump stocks remain prohibited under New Jersey law, and this decision has no impact on our law, which I will continue to enforce to the fullest extent. There is no valid reason for any law-abiding citizen to own a device capable of causing extreme bloodshed,” he added.