Garland v. Cargill and why an agency cannot rewrite a law by redefining a word

Suppose your bank sent you a letter that said: "We have decided that the word 'Tuesday' now includes Wednesday. You are late on your payment. Please remit, with interest." You would not call that interpretation. You would call a lawyer. And the lawyer would tell you that a word means what it meant when the contract was signed, not what the lender finds convenient this morning.

Now swap the bank for a federal agency, swap the contract for a criminal statute, and swap "late on your payment" for "ten years in a federal prison." That is the story of Garland v. Cargill, and it is one of the cleanest lessons in how our government is supposed to work that the Supreme Court has handed us in years. It is not a story about whether you like bump stocks. It is a story about who gets to write the law. The answer, as the Founders had it, is Congress. Not the ATF. Not the Justice Department. Not the President with a pen and a phone.

The statute everything turns on

Start with the text, because the text is where this case was decided.

The National Firearms Act of 1934 regulates certain weapons, with a tax and a registry, and the most heavily regulated are machine guns. The statute's definition, in what is now 26 U.S.C. 5845(b), says that a "machinegun" is any weapon that shoots, or is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger. The definition also sweeps in the frame or receiver of such a weapon and any part designed and intended solely and exclusively, or combination of parts, for converting a weapon into a machine gun. (The story of the 1934 Act is in Why the National Firearms Act of 1934 taxed guns instead of banning them.)

Then came 1986. Congress banned the possession or transfer of new machine guns by civilians, with exceptions, in the Firearm Owners Protection Act. (See How the 1986 Firearm Owners Protection Act passed with a machine gun ban.) Add it up and you get a stark rule. If an item is a machine gun under the statute, owning it is a serious federal felony. The penalty under the National Firearms Act, 26 U.S.C. 5871, is up to ten years in prison and a fine.

So the three words that matter are single function of the trigger. Remember them. The entire case is about what they mean.

What a bump stock does

A bump stock is a stock, the part of a rifle that rests against your shoulder, built to slide back and forth. On a semiautomatic rifle, each pull of the trigger fires one shot. Pull again, fire again. A bump stock lets the whole rifle recoil backward into the shoulder and then slide forward again, so the trigger bumps against the shooter's stationary finger. If the shooter keeps forward pressure on the barrel and keeps the finger in place, the rifle can cycle rapidly, firing a shot each time.

The company that made the best-known version was Slide Fire. And this is the part the government would rather you didn't dwell on: the ATF approved it. Starting in 2008, the ATF's firearms technology staff wrote letters concluding that bump-stock-type devices were not machine guns, because the rifle still fired one shot per trigger pull. The agency repeated that conclusion in later classification letters for other models. For about a decade, the people charged with enforcing the law told manufacturers and buyers, in writing, that this device was legal.

What changed

On October 1, 2017, a gunman opened fire from a hotel in Las Vegas on a concert crowd. Fifty-eight people were killed. Some of the rifles used had bump stocks. The country was horrified, and it should have been.

What happened next is the part worth studying. Congress held hearings and considered bills. It did not pass one. The Trump administration, in February 2018, directed the Justice Department to propose regulations that would treat devices that turn legal weapons into machine guns as machine guns. The ATF then did what an agency does when a legislature won't act. It reversed itself. In a final rule published on December 26, 2018, it announced that its earlier letters were wrong, that bump stocks were machine guns under the statute, and that anyone who owned one had until March 26, 2019, to destroy it or turn it in. After that date, possession would be a felony.

Look at what happened there. Not a word of the statute changed. The device did not change. The ATF's letters from the previous decade did not change. Only the agency's opinion changed, and with it the consequences for every owner who had bought the item legally, in reliance on the government's own approval. I don't know about you, but I call that something other than law enforcement.

The case

Michael Cargill, an Austin, Texas, gun shop owner, turned in two bump stocks under protest and sued. After a long trip through the courts, which included a divided en banc decision at the Fifth Circuit in his favor, the Supreme Court heard the case and decided it on June 14, 2024, in a 6-to-3 opinion written by Justice Clarence Thomas. Chief Justice Roberts and Justices Alito, Gorsuch, Kavanaugh and Barrett joined him.

The reasoning is short enough to put in numbered premises, which is how I like it.

1. The statute defines a machine gun as a weapon that fires more than one shot "by a single function of the trigger."
2. The "function" of the trigger, as the Court read the mechanics, is the movement of the trigger itself: the pull. A semiautomatic rifle fires one shot per function of the trigger.
3. A bump stock does not change the trigger or how it functions. It harnesses the recoil of the rifle so that the shooter's finger re-engages the trigger quickly. Each shot still requires a separate trigger function, produced by the rifle's movement against the shooter's finger.
4. Therefore a rifle with a bump stock does not fire more than one shot per single function of the trigger, and a bump stock is not a "machinegun."
5. If Congress wants to ban bump stocks, Congress can do it. The ATF cannot do it by changing what a word means.

Think about premise five for a second. It is the whole case in a sentence.

The concurrence that says the quiet part out loud

Justice Alito wrote a short concurring opinion that deserves to be read by every member of Congress. He agreed with the result and then said, in effect: this is a problem for you. The Las Vegas massacre was a tragedy, he wrote, and a bump stock is functionally close to a machine gun. If Congress wants such a device treated that way, "there is a simple remedy," and it is to amend the law.

That is not a throwaway line. That is the constitutional design. Article I begins: "All legislative Powers herein granted shall be vested in a Congress of the United States." The first article, in the first sentence. If you do not like what the statute says, you have a lawful, democratic, accountable way to change it, and that way runs through the House and the Senate. (For the broader point, see Congress Should Write the Laws, and Other Radical Ideas From Article I.)

The dissent, stated at full strength

Justice Sotomayor, joined by Justices Kagan and Jackson, dissented, and her dissent is not silly. Here is the best version of it.

A bump-stock-equipped rifle, she wrote, does what a machine gun does. The shooter pulls once, holds the position, and the rifle fires continuously, "automatically," as the statute puts it. The ordinary person looking at the result would call it a machine gun. Congress banned machine guns because they can kill many people quickly, and that is exactly what the Las Vegas shooter used. Reading the statute so narrowly that it excludes a device built to produce that effect defeats the law's purpose. Her image was the old duck test: when something looks like, sounds like and does what a duck does, call it a duck.

That is a serious argument, and it appeals to a serious instinct: that law should be read to achieve its evident purpose. So let me answer it point by point.

1. A statute is its words, not its purpose. Congress does not vote on purposes. It votes on text. The text said "single function of the trigger." If lawmakers wanted a broader reach, they could have written "single pull," or "continuous firing," or "any device that increases the rate of fire." They didn't. A judge who rewrites the text to achieve the result he prefers is doing the legislature's job.
2. This is a criminal statute. The ATF's rule makes you a felon for owning an accessory the agency itself had once called legal. Criminal laws must give fair notice of what is forbidden. The Court's longstanding rule of lenity says that a genuinely unclear criminal law is read in the defendant's favor, not the prosecutor's.
3. The ATF told the public the opposite for a decade. If the duck test is so obvious, why did the agency's own experts miss it for ten years? It is hard to claim that the meaning is plain when the people charged with enforcing it read it the other way over and over.
4. Purpose cuts both ways. If purpose can expand a statute to cover what lawmakers did not write, then it can expand any statute. And the next administration will use that power in the direction you like least.

The lesson for every administration

This is the part conservatives should take to heart, and I'd say it to a Republican White House exactly as I'd say it to a Democratic one.

The 2018 rule was issued under President Trump, a Republican. Many of the people who cheered Cargill were conservatives, and rightly. But the principle cuts across parties. If an agency can change the meaning of a statute because the political winds shifted, then every law is only as stable as the next election. A rule against bump stocks today is a rule against some other lawful thing tomorrow, and the precedent is the same. Today's friendly administration is tomorrow's unfriendly one. The only protection against a government that can rewrite laws at will is a Constitution that says it cannot.

That is why this decision belongs in the same family as the end of deference to agency readings of statutes. Two weeks after Cargill, the Court decided Loper Bright, which ended the Chevron doctrine, and the thread running through both is the same: judges, not agencies, say what the law means. (See Chevron Is Gone, and Here Is What Loper Bright Changed for Everyone.) It is also why the five-question test in A Five-Question Constitutional Test You Can Run on Any Federal Law begins by asking who wrote the rule. And it is the same moral as Equal Under the Law Means the Rule Applies to the People in Charge: a government that bends its own rules for good reasons will bend them for bad ones.

A fair reader will ask: what about the victims? Isn't there something to be said for an agency that acts when Congress won't? The answer is no, and the reason is the whole point of a republic. Congress's failure to act is not a loophole. It is an answer. The legislative process is slow on purpose, and it gets slower when the country is divided. That friction protects you when the other side is in power. You cannot keep the benefit of it and discard it when you're annoyed.

What this means for gun owners and for everyone else

For the owner who was told to destroy a lawfully bought item, the case is vindication. For the person who wants a law against bump stocks, the case is a map: write it, pass it, and let it be debated in public, where it can be voted on. A statute that bans these devices outright would answer the court's concern in one sentence. The point is that the sentence has to come from Congress.

For the rest of us, it is a reminder to ask the question before we cheer. When an agency does something we like, ask: what statute authorizes this, and who voted for it? If the answer is "nobody," then we have not won anything. We've only borrowed power we will have to give back.

The bottom line

• Garland v. Cargill, decided June 14, 2024, held 6 to 3 that a bump stock is not a "machinegun," because a rifle with one still fires one shot per function of the trigger.
• The ATF had approved these devices in writing for about a decade, then reversed itself in a December 2018 rule without a change in the statute. Reversal by reinterpretation is not lawmaking.
• If you want a federal ban on a device, the remedy is Article I: persuade the House and the Senate. Justice Alito said so in plain terms.
• Keep the principle bigger than the product. The agency that can redefine a word for a policy you like can redefine it for a policy you don't.
• Next time an agency announces a "clarification" that changes what is a crime, ask what statute it rests on and who voted for it. Then call your representative.