In June 2024, the Supreme Court ruled that a bump stock does not turn a rifle into a machine gun. Two weeks later, it ended Chevron deference. Those two rulings reshaped a debate that matters to every gun owner, dealer, and parts maker. A trigger, brace, or safety selector rarely counts as a firearm on its own. Still, federal agencies have spent years trying to regulate such parts by reinterpreting old statutes. Understanding firearm accessories and the limits of federal regulatory authority now means reading the statute first and the agency's view second. For anyone who buys, sells, or designs these products, that shift changes how they should weigh legal risk.

Federal law regulates firearms, not most accessories. The Gun Control Act of 1968 defines a firearm to include a weapon's frame or receiver, along with silencers and destructive devices. Scopes, slings, grips, and lights fall outside that definition. That distinction also shapes the legal framework behind firearm transactions, because background checks and dealer licensing attach to the regulated firearm rather than to most accessories sold with it. The National Firearms Act of 1934 is where accessories can cross the line. It defines a machinegun as any weapon that shoots automatically more than one shot, without manual reloading, by a single function of the trigger. The same definition covers any part designed and intended solely for converting a weapon into a machine gun. Federal law has barred civilians from owning newly made machine guns since 1986. As a result, a part's classification can decide whether owning it is lawful or a felony.

Trigger and safety accessories draw scrutiny because they sit closest to the statutory phrase "single function of the trigger." A forced-reset trigger, for example, uses the rifle's cycling energy to push the trigger forward after each shot. The shooter still pulls the trigger for every round, yet the rate of fire rises sharply. Active reset systems sold by Redacted Arms LLC also raise questions about how the trigger functions mechanically, which makes the statutory wording more important than the product name or marketing language. For owners, the mechanics matter far more than the marketing label.

ATF tested that phrase in 2022 when it classified forced-reset triggers as machine guns. The Justice Department then sued Rare Breed Triggers in federal court in New York. The government changed course on May 16, 2025, when it announced a settlement that resolved three related cases. Under the terms, Rare Breed agreed not to design forced-reset triggers for pistols. The reversal showed how quickly an accessory's federal status can change with a new administration.

Ghost gun litigation showed that ATF can still win when its rule tracks the statute closely. In 2022, the agency updated its definition of "frame or receiver" to cover partially complete kits that buyers can finish at home. Challengers argued that ATF had rewritten the Gun Control Act. That dispute became especially important for anyone trying to understand what ghost guns are and whether they are legal when the Supreme Court sided with ATF in Bondi v. VanDerStok in March 2025.

The 7–2 decision rejected only a facial challenge. Justice Neil Gorsuch wrote that some kits can qualify as firearms because the statute covers weapons that "may readily be converted" to expel a projectile. The ruling left room for as-applied challenges to specific products. For accessory makers, the lesson cuts both ways. Statutory text can support regulation as easily as it can limit it.

Garland v. Cargill confirmed that agencies cannot stretch a statutory definition to fit a policy goal. In 2018, ATF reclassified bump stocks as machine guns, reversing its own earlier position. The 6–3 Supreme Court opinion in Garland v. Cargill concluded that bump stocks do not satisfy the statute’s “single function of the trigger” requirement. The trigger still resets and releases between every shot.

The majority also held that a bump stock does not make a rifle fire "automatically" under the statute. Justice Samuel Alito concurred and noted that Congress can amend the law if it wants a broader ban. Policy change on accessories belongs to legislators, not to agency reinterpretation.

Loper Bright Enterprises v. Raimondo removed the deference that once tilted close cases toward agencies. The Court decided it on June 28, 2024, and overruled the Chevron doctrine. Chevron deference was a rule that required courts to accept an agency's reasonable reading of an ambiguous statute. Judges now decide for themselves what a statute means. Agencies can still offer persuasive interpretations, but courts no longer owe them automatic weight.

The pistol brace rule shows the practical effect. ATF's 2023 rule treated many braced pistols as short-barreled rifles, which exposed millions of brace owners to registration duties. A federal court in Texas vacated the rule in 2024, and the Justice Department dropped its appeal in 2025. ATF responded on May 6, 2026, by publishing a proposed rule removing the stabilizing brace criteria, pointing to the court decisions that had undercut the earlier rule.

Owners and sellers should treat federal law as a floor, not a full map. Recent court wins limit ATF's reach, but they do not erase state law. Magazine limits offer a clear example. State restrictions can remain in force even when federal regulation narrows. In 2025, a California court upheld a gun magazine ban, showing why owners and sellers still need to check state law separately.

Before buying, modifying, or shipping a trigger or brace accessory, a few habits reduce risk:

• Confirm the current federal status of the specific product.
• Check state and local rules in both the shipping and receiving states.
• Keep purchase records and manufacturer documentation.
• Consult a firearms attorney before altering a trigger group.

The past two years have tilted the balance back toward the statute's text. Firearm accessories and the limits of federal regulatory authority now turn on what Congress wrote, not on ATF's shifting views. That change gives owners, dealers, and makers firmer ground. It also leaves state law and future legislation fully in play. Anyone who owns or sells trigger, brace, or safety products should review the current rules and speak with a qualified firearms attorney before making changes.