Here’s what to know about the hearing.

The Supreme Court is expected to hear arguments on Wednesday over whether the Trump administration acted lawfully in banning bump stocks, attachments that enable a semiautomatic rifle to fire faster, rivaling the speed of a machine gun.

The ban, enacted after a gunman in Las Vegas opened fire on a country music festival in 2017, prohibits the sale and possession of the accessory.

The case does not turn on the Second Amendment. Instead it is one of a number of challenges aimed at limiting the power of administrative agencies — in this instance, the Bureau of Alcohol, Tobacco, Firearms and Explosives.

A ruling against the agency could affect its ability to regulate firearms and accessories.

Here is what else to know:

• The bump stock is not a gun — it’s a gun part or accessory. But if the court deems it can be used to make a gun into a “machine gun,” then it can be banned as part of a category heavily regulated by the A.T.F. Machine guns have been banned since the 1930s, and since the 1960s, the federal government extended that prohibition to parts that transform weapons into machine guns. Until 2018, bump stocks were legal to buy and own, based on the argument that they increased the speed of a gun by sliding it back and forth to rapidly pull the trigger, not by a single squeeze required for a machine gun.

• The situation changed after the deadliest mass shooting in modern American history. In October 2017, a gunman, perched in a Las Vegas hotel room, sprayed more than 1,000 rounds over about 11 minutes, killing 60 and wounding hundreds. In his arsenal were guns outfitted with bump stocks.

• After the shooting, lawmakers, including several leading Republicans, voiced support for banning the device. Even the National Rifle Association endorsed tighter restrictions. Political pressure escalated after the school shooting in Parkland, Fla., prompting President Donald J. Trump to promise to ban bump stocks. (The Parkland gunman did not use a bump stock.)

• Initially, Justice Department officials had said the executive branch could not ban bump stocks without action by Congress. But it ultimately reversed course and decided that it could ban the devices without action by Congress, saying that bump stocks fell within the definition of a machine gun.

• The government asked the Supreme Court to intervene after the U.S. Court of Appeals for the Fifth Circuit declared the ban unlawful.

• In its briefs, the government argued that bump stocks fit within that definition and should remain banned. “Like other machine guns, rifles modified with bump stocks are capable of firing hundreds of bullets per minute,” wrote Solicitor General Elizabeth B. Prelogar. If the Fifth Circuit’s decision were to stand, she wrote, “its consequences are likely to reverberate nationwide.”

• Lawyers for the man challenging the bump stock ban, a Texas gun shop owner named Michael Cargill, disagreed with the government’s analysis and argued the federal agency had overstepped. “A weapon is not a machine gun if something more is required of the shooter than a single function of the trigger to produce more than one shot,” according to a brief by the challengers.