UNITED STATES COURT OF APPEALS FOR THE SIXTH CIRCUIT

┐ SCOTT A. HARDIN, │ Plaintiff-Appellant, │ │ v. > No. 20-6380 │ │ BUREAU OF ALCOHOL, TOBACCO, FIREARMS AND │ EXPLOSIVES, an agency of the Department of Justice; │ STEVEN M. DETTELBACH, Director Bureau of Alcohol, │ Tobacco, Firearms, and Explosives; UNITED STATES │ OF AMERICA; MERRICK B. GARLAND, Attorney │ General, in his official capacity as Attorney General of │ the United States, │ Defendants-Appellees. │ ┘ Appeal from the United States District Court for the Western District of Kentucky at Louisville. No. 3:19-cv-00056—David J. Hale, District Judge.

Argued: January 19, 2023

Decided and Filed: April 25, 2023

Before: GILMAN, McKEAGUE, and BUSH, Circuit Judges. _________________

COUNSEL ARGUED: Jason Todd Hardin, HARDIN LAW, PLLC, Louisville, Kentucky, for Appellant. Brad Hinshelwood, UNITED STATES DEPARTMENT OF JUSTICE, Washington, D.C., for Appellees. ON BRIEF: Jason Todd Hardin, HARDIN LAW, PLLC, Louisville, Kentucky, J. Allan Cobb, COBB LAW PLLC, Louisville, Kentucky, for Appellant. Brad Hinshelwood, Abby C. Wright, Kyle Edwards, UNITED STATES DEPARTMENT OF JUSTICE, Washington, D.C., for Appellees.

GILMAN, J., delivered the opinion of the court in which McKEAGUE, J., joined. BUSH, J. (pp. 10–13), delivered a separate opinion concurring in the judgment. No. 20-6380 Hardin v. ATF, et al. Page 2

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OPINION _________________

RONALD LEE GILMAN, Circuit Judge. The placement of a bump stock on a semiautomatic rifle causes the rifle to function essentially like a machinegun by dramatically increasing the rate of fire. And the possession of a machinegun is a criminal offense under the Gun Control Act of 1968. This raises the question of whether a bump stock is a machinegun “part” as defined by the National Firearms Act of 1934. The question is a close one on which reasonable jurists have disagreed, a disagreement caused by ambiguities in how the applicable statute defines the term “machinegun.”

An Act of Congress could clear up the ambiguities, but so far Congress has failed to act. The Bureau of Alcohol, Tobacco, Firearms and Explosives (the ATF) has been on both sides of this issue, with its current regulation (the Rule) banning bump stocks as a machinegun part. In this situation, the rule of lenity that is applicable to criminal offenses requires us to rule in favor of Hardin. We therefore REVERSE the judgment of the district court and REMAND for further proceedings consistent with this opinion.

I. BACKGROUND

The Gun Control Act provides that “it shall be unlawful for any person to transfer or possess a machinegun.” 18 U.S.C. § 922(o)(1). It incorporates by reference (see id. § 921(a)(24)) the definition of a machinegun as set forth in the National Firearms Act, which reads as follows: