[4] Since enactment, this law requires the payment of a $200 excise tax, accompanied with vetting by the ATF, before a person can legally make, possess, or transfer a machine gun, short-barreled rifle or shotgun, silencer, destructive device, or any other weapon (AOW).

In the 2017 Las Vegas shooting, a gunman using semiautomatic rifles equipped with bump stocks fired hundreds of rounds into a crowd, killing 58 people,[a] wounding more than 500 others.

[6] In the wake of the Las Vegas shooting, ten states had banned bump stocks, and while there was legislation introduced in the U.S. Congress, the bills did not pass due to partisan politics.

[7] The Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) also had not taken action, having treated bump stocks outside the definition of "machine guns" in the NFA.

[7] Following the public commenting period, the ATF proceeded to publish a new rule in December 2018 to repudiate its previous stance and "clarify" that bump stocks were machine guns as defined under the National Firearms Act.

[11] The plaintiff in the case was Michael Cargill, owner of Central Texas Gun Works, who in 2018 purchased two bump stocks a few months before the ATF published its new rule.

The majority opinion, written by Justice Clarence Thomas, stated that under the National Firearms Act, bump stock attachments did not qualify as machine guns since, even if they did fire more than one round per trigger pull, they did not do so automatically, and thus could not be regulated by the ATF through administrative action, and that only congressional legislation could empower the agency with such authority.

[19] Thomas also identified that prior to the Las Vegas shooting, the ATF across multiple administrations had previously declined to declare bump stocks as machine guns, but "abruptly reversed course" in its wake.

Alito wrote the following: "There can be little doubt that the Congress that enacted [the National Firearms Act] would not have seen any material difference between a machinegun and a semiautomatic rifle equipped with a bump stock.

"[30][31][32] Although it was under his administration that the ATF final rule on bump stocks first came into effect, former-President Donald Trump stated through a campaign spokesperson that "the [Supreme] Court has spoken and their decision should be respected".

[33] After the ruling, a bill[b] with bipartisan support was introduced before the Senate to outlaw semi-automatic firearms equipped with devices (including bump stocks) that increase their rate of fire.