AR-15 laws: a federal overview

Last reviewed October 26, 2026 · 11 sources

Short answer: At the federal level, a standard semi-automatic AR-15 is regulated as an ordinary rifle under 18 U.S.C. chapter 44 and 27 CFR part 478. The stricter National Firearms Act (NFA) rules apply when the weapon falls into an NFA category, such as a machinegun or a rifle with a barrel shorter than 16 inches. [26 U.S.C. § 5845, (a)] States add their own rules, and those vary widely.

National Firearms Act (NFA)

The National Firearms Act of 1934 is codified at 26 U.S.C. chapter 53. [Cargill (2024)] [26 U.S.C. ch. 53] Its definition of “firearm” covers specific categories, including:

• “a rifle having a barrel or barrels of less than 16 inches in length”
• “a weapon made from a rifle if such weapon as modified has an overall length of less than 26 inches or a barrel or barrels of less than 16 inches in length”
• “a machinegun”
• “any silencer”

[26 U.S.C. § 5845, (a)] ATF’s NFA regulations are at 27 CFR part 479. [27 CFR pt. 479]

Federal definitions and dealer rules (18 U.S.C. chapter 44)

• Firearm includes “the frame or receiver of any such weapon.” [18 U.S.C. § 921, (a)(3)] For AR-15/M-16 variants, the receiver is the lower receiver. [27 CFR § 478.12]
• Semiautomatic rifle is a repeating rifle that fires one cartridge per separate pull of the trigger. [18 U.S.C. § 921, (a)(29)]
• Background checks: licensed dealers, manufacturers, and importers must generally contact NICS before transferring a firearm to an unlicensed person. [18 U.S.C. § 922, (t)(1)]

ATF’s implementing regulations are at 27 CFR part 478. [27 CFR pt. 478]

Semi-automatic rifles vs machineguns

A “machinegun” is “any weapon which shoots, 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 covers conversion parts. [26 U.S.C. § 5845, (b)] Transferring or possessing a machinegun is unlawful except for government use and for machineguns lawfully possessed before § 922(o) took effect. [18 U.S.C. § 922, (o)]

The 1994 federal law and its expiry

The Violent Crime Control and Law Enforcement Act of 1994 (Pub. L. 103-322) was enacted on September 13, 1994. Title XI, Subtitle A, the “Public Safety and Recreational Firearms Use Protection Act,” made it unlawful to manufacture, transfer, or possess a “semiautomatic assault weapon,” subject to exceptions. That included firearms otherwise lawfully possessed when the law took effect. The definition listed the “Colt AR-15” by name and included a features test for semi-automatic rifles. [Pub. L. 103-322, § 110102] Under § 110105, the subtitle took effect on enactment and was “repealed effective as of the date that is 10 years after that date.” [Pub. L. 103-322, § 110105]

Key Supreme Court cases

• District of Columbia v. Heller (2008): the Court held that “the Second Amendment protects an individual right to possess a firearm unconnected with service in a militia, and to use that arm for traditionally lawful purposes, such as self-defense within the home.” [Heller (2008)]
• New York State Rifle & Pistol Assn. v. Bruen (2022): the Court held that New York’s proper-cause requirement for carry licenses violated the Fourteenth Amendment “by preventing law-abiding citizens with ordinary self-defense needs from exercising their Second Amendment right to keep and bear arms in public for self-defense.” [Bruen (2022)]
• Garland v. Cargill (2024): the Court held that ATF exceeded its statutory authority by classifying bump stocks as “machineguns” under 26 U.S.C. § 5845(b). [Cargill (2024)]

State laws vary

Recent changes