On October 8, the Supreme Court will hear oral arguments on an enormously consequential question: Are “ghost guns”—untraceable weapons assembled from parts or kits—“firearms” within the meaning of the Gun Control Act of 1968, and therefore subject to regulations on the sale of firearms? Congress answered this question after assassins whose qualifications to buy guns were never reviewed bought the rifles that killed John F. Kennedy and, five years later, his brother Robert, and Martin Luther King, Jr. If the text and history of the law are as crucial to the Supreme Court justices as they claim, they should uphold the government regulation in this case.

In 1963, Lee Harvey Oswald assassinated President Kennedy with a rifle ordered through a catalog with a fake name and address. In 1968, while Congress was working on a law that would prevent similar tragedies, Senator Robert Kennedy of New York and Dr. Martin Luther King, Jr. were both killed by assassins who were not legally permitted to purchase guns.

Just hours after the Democratic presidential candidate’s assassination in June 1968 in California, his Congressional colleagues called for the passage of stalled legislation—legislation that the junior senator from New York had earlier said would “save hundreds of lives in this country.” Preventing what President Lyndon Johnson called “mail-order murder” was the law’s goal. While Congress debated gun control legislation between the two Kennedy assassinations, a second concern emerged—“starter pistols,” the inexpensive and easy-to-purchase track-and-field guns designed to fire blanks at the beginning of footraces but which could be converted into lethal weapons. Congress’s goal was to stop the dangerous deception of gun makers who were trying to evade the law.

In writing the Gun Control Act, Congress chose language broad enough to encompass the modified starter pistol of 1968 and the 3D-printed ghost gun of 2024. The law broadly defines a “firearm” (and thus subject to federal regulations) as “any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive” and “the frame or receiver of any such weapon.”

In 2021, the Bureau of Alcohol, Tobacco, Firearms and Explosives issued regulations making explicit that nearly complete frames and receivers—the central components of guns—and weapon parts kits come within the GCA’s definition of “firearm” and thus can be regulated. But ghost gun manufacturers sell “80 percent frames” that can be converted to full functionality with no more than a few swipes of a craft knife or a drill. Likewise, weapon parts kits are available on the market that can be converted into fully functional firearms in less than an hour. These products fall under the GCA’s definition of a firearm but not according to the Fifth Circuit Court of Appeals. In November 2023, it held that a near-complete frame or receiver was no different than a useless lump of plastic. According to that court, something isn’t “readily” converted if the conversion takes longer than 30 seconds. The majority on the Fifth Circuit tartly dismissed ATF’s conclusion that the nearly-complete frames and receivers and parts kits are “firearms” as a power grab, allowing the agency to regulate anything “more refined” than “primordial ooze.”

At the Supreme Court, the gun manufacturers that challenged the ATF regulations doubled down on their argument, using metaphors—their gun kits are to guns what groceries are to dinner, or batter to cake, or grapes to wine. In their briefs, they argued that it doesn’t matter how close to completion the gun is. If it’s not already assembled into a finished weapon, it’s not a weapon, so the law doesn’t apply. This argument is like claiming that Betty Crocker is not in the cake business.

The gun manufacturers also argued that a “converted” object has to go from a finished weapon to a different finished weapon for the law to kick in. This argument is directly at odds with the law’s text. The terms “readily” and “converted” meant the same thing in 1968 as today. When an amateur working at home transforms a kit from an unfinished, disassembled state into a finished state with quick efficiency and a fair degree of ease, that person “readily” “converts” the kit into a firearm. And it doesn’t matter if a conversion takes 30 seconds or three days.

The question is whether the kits can be converted with a fair degree of ease, and there’s no doubt that they can be. Indeed, Congress used broad language to allow regulation of kits and devices that could easily transformed into lethal weapons. Thus, to answer the question, the justices need only follow the answer Congress has given them.