On June 14, 2024, the Supreme Court handed down Garland v. Cargill, 602 U.S. 406 (2024), striking down the ATF’s 2018 bump stock ban in a 6–3 decision. The Court held that bump stocks do not transform semi-automatic rifles into “machineguns” under the National Firearms Act. Attorney General Merrick Garland had defended a rule that required roughly 500,000 Americans to destroy or surrender legally purchased accessories on 90 days’ notice with no compensation. The rule was unlawful from the beginning. The Supreme Court finally confirmed it.
What the NFA’s Text Actually Says
The National Firearms Act defines “machinegun” as any weapon that fires more than one round “by a single function of the trigger.” 26 U.S.C. § 5845(b). Congress inserted that language when it amended the statute through the Hughes Amendment in 1986. It is a mechanical definition. It does not say “anything that produces a high rate of fire.” It does not say “functional equivalents of machine guns.” It refers to a specific mechanical event: a single trigger actuation producing multiple shots.
A rifle equipped with a bump stock does not do that. The bump stock redirects recoil energy to assist the shooter’s trigger finger in actuating the trigger in rapid succession — but each shot requires a distinct, separate trigger function. The device accelerates the rate of individual trigger pulls by harnessing the rifle’s own recoil against the shooter’s stationary finger. It does not mechanically collapse multiple shots into one pull.
Justice Clarence Thomas, writing for the majority joined by Chief Justice Roberts and Justices Alito, Gorsuch, Kavanaugh, and Barrett, applied the plain statutory text and found exactly that. The NFA asks a specific mechanical question. Bump stocks give a mechanically clear answer. The majority followed the text to its correct conclusion.
ATF Substituted Its Judgment for Congress’s Words
The ATF’s 2018 rule reinterpreted “single function of the trigger” to mean “anything that enables firing at the rate of a machine gun.” That is not statutory interpretation — it is statutory rewriting. Congress chose a precise mechanical test. ATF replaced it with a practical-effect test that Congress never enacted.
Agencies do not write the laws they enforce. When Congress defines a term, the agency’s task is to apply that definition, not to improve it because the agency believes a different definition would better advance policy goals. The Fifth Circuit, sitting en banc in Cargill v. Garland, 57 F.4th 447 (5th Cir. 2023), had already recognized this before the Supreme Court took up the case, splitting with the D.C. Circuit’s contrary holding in Guedes v. ATF, 920 F.3d 1 (D.C. Cir. 2019).
The rule of lenity independently disposes of any argument from ambiguity. Criminal statutes must be resolved in favor of defendants, not the government. The NFA imposes criminal penalties. If the definition of “machinegun” were genuinely unclear — and it is not — the tie breaks in favor of the citizen, not the agency seeking to expand criminal liability. Nearly 500,000 Americans who surrendered or destroyed their bump stocks between 2018 and 2024 did so under a rule that had no valid legal foundation.
The Dissent’s Results-Oriented Logic
Justice Sonia Sotomayor dissented, joined by Justices Kagan and Jackson. The dissent’s core argument is straightforward: bump stocks produce the same practical result as automatic fire — rapid volleys at machine-gun rates — so they should be treated as machine guns. Congress surely intended the NFA to reach devices that replicate automatic fire’s danger.
The problem is unmistakable. The NFA does not regulate “practical danger equivalent.” It defines machine guns by trigger function. Congress made that choice deliberately. If Congress believes the definition leaves a gap, Congress can amend the statute. That is precisely the mechanism the Constitution provides for closing statutory gaps the legislature finds inadequate.
The dissent’s functional-equivalence reasoning also has no principled limiting principle. If anything that allows fire at machine-gun speeds is a machine gun, then polished match triggers, spring-operated trigger shoes, and even exceptionally well-practiced trigger technique become potential NFA violations. That is a regulatory regime with no logical boundary, governed by agency assessment of “effective firing rate” rather than by the text Congress wrote. The majority correctly refused to endorse it.
What Cargill Means Going Forward
Garland v. Cargill is not merely about bump stocks. It is a restatement of a principle that courts have struggled to enforce consistently: agencies enforce statutes they did not write, and they cannot exceed the authority those statutes confer.
Every ATF regulation built on creative statutory interpretation now faces heightened judicial risk. The bump stock rule was the product of an agency that believed its practical judgment about danger should override a statutory text Congress deliberately chose. The Supreme Court disagreed. That reasoning applies to any ATF rule that substitutes the agency’s preferred policy outcome for the actual words of the NFA or Gun Control Act.
The decision also pairs naturally with the post-Bruen environment. Bruen demands that gun regulations be tested against the nation’s historical tradition of firearms regulation. Cargill demands that ATF regulations be tested against the actual statutes Congress enacted. Together, they narrow the space for unilateral ATF action. That is exactly where the space should be.
This article is based on analysis by Professor Mark W. Smith, constitutional attorney and Host of the Four Boxes Diner 2nd Amendment channel. Watch the original video here. This does not constitute legal advice.