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ATF: What Is a Gun?

Making a decision about what is or is not a “firearm” under the law would seem to be a fairly straightforward process, but recent controversy about the regulations used by the Federal Bureau of Alcohol, Tobacco, Firearms, and Explosive (“ATF”) has shown that the definition of a gun is not nearly as clear as it seems.

The legal definition of a firearm is laid out in the 1968 Gun Control Act. That law’s definition includes not only what most people would think of as a gun but also “the frame or receiver of any such weapon.” 18 U.S.C. § 922(a)(3). Defining what a receiver or frame is, however, was left up to regulating agencies – in this case, the ATF. The ATF defined a receiver as having three elements: hammer, bolt or breech-lock, and firing mechanism. This “receiver,” even without the rest of the weapon, is legally considered a firearm in itself.

The problem with this definition, according to former ATF agent and firearms expert Dan O’Kelly, is that roughly 60 percent of the guns in America do not have a single part that fits this description. As a practical matter, this means the ATF should not be able to charge a person with possessing a firearm if they have a piece of a weapon that does not exactly fit the regulatory description. The problem that has arisen, and has led O’Kelly to testify against his former employer, is that the ATF is pursuing prosecutions in cases where the firearm part in question does not fit the legal definition.

The part at issue belongs to an AR-15 assault rifle. This type of rifle does not have a stereotypical receiver. Instead, it splits the functions of a receiver across two parts—an upper and lower receiver, neither of which meet all three factors in the ATF’s own regulatory definition.

The ATF administratively decided to classify the lower receiver as the legally prohibited part, despite O’Kelly’s protests while still serving as an agent, and the bureau launched legal actions based on this administrative decision.

It is unclear how long the ATF has followed this policy or how many prosecutions have been undertaken, but starting in 2014, O’Kelly began to testify on behalf of defendants facing prosecution for the possession of AR-15 lower receivers. In the first three of these cases, the defendants prevailed, but the government withdrew its charges before a precedent-setting decision was made. Then, in late 2019, the ATF and federal prosecutors risked the setting of a precedent in an Ohio court where two felons were charged with possession of lower receivers.

Dan O’Kelly testified at an evidentiary hearing for the defendants’ motion to dismiss, as did a current ATF agent. Despite government protests that they had broad discretion to interpret regulation, the court ruled that when the text of a regulation is clear and the action of the agency runs counter to that text, the agency’s action cannot stand. Specifically, if the defendants do not possess that part of a firearm that is defined as illegal, the agency cannot arbitrarily alter the standard to charge them with a crime.

O’Kelly takes no pleasure in being in an adversarial relationship with his former employer, nor does he like seeing criminals go free. He says the ATF needs to redefine the legal bar for what a receiver is. But, until then, when called to testify, he will tell the truth. 


Sources:, United States v. Rowold, 2019 U.S. Dist. LEXIS 217016 (N.D. Ohio 2019)

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United States v. Rowold



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