DENVER, CO (October 13, 2020) — Today, Firearms Policy Coalition (FPC) and Firearms Policy Foundation (FPF) announced the filing of an important legal brief in Aposhian v. Barr, a bump-stock ban case on appeal to the en banc Tenth Circuit Court of Appeals. The Aposhian brief was authored by FPC Director of Research Joseph Greenlee, and coauthored by George Mocsary, a law professor at the University of Wyoming College of Law, and Erik Jaffe, an expert in appellate and Supreme Court practice focusing on constitutional law from the Washington, D.C. boutique firm Schaerr | Jaffe LLP. The brief is available online at

After consistently issuing letter rulings declaring that bump-stocks are not machineguns, the ATF backtracked and declared that “bump-stock type” devices were machineguns in a Final Rule issued on December 26, 2018. Consequently, the ATF ordered Mr. Aposhian to destroy his bump-stock device by March 26, 2019, or face up to 10 years imprisonment. Mr. Aposhian challenged the ATF’s Final Rule, alleging that Congress—not an administrative agency—should define criminal laws, and that, if Congress’s definition of the term “machinegun” was vague, the rule of lenity (which requires that a court interpret an ambiguous law in favor of the defendant) should apply rather than Chevron deference (which grants deference to an agency’s interpretation of a law).

Previously, a three-judge panel of the Tenth Circuit ruled against Aposhian in his appeal from a motion for a preliminary injunction, but the court agreed to rehear the case en banc. A key issue before the court is whether, if Congress’s definition of “machinegun” is ambiguous, the court should apply the rule of lenity or Chevron deference to resolve the ambiguity. 

FPC and FPC have a special interest in the outcome of the case because each organization is challenging the ATF’s Final Rule in their own cases, Guedes v. Bureau of Alcohol, Tobacco, Firearms, & Explosives and Firearms Policy Coalition, Inc. v. Whitaker, the first such cases in the nation. After a trip to the Supreme Court, in which Justice Gorsuch provided important insights in a statement respecting the denial of certiorari, the Guedes case is currently in final phases on cross motions for summary judgment. The FPC case is on appeal to the D.C. Circuit Court of Appeals. 

FPC and FPF’s brief argues that the rule of lenity should apply because it is a critical protection of several fundamental constitutional principles, including due process and the separation of powers. Conversely, the application of Chevron deference to a criminal law violates the separation of powers by taking lawmaking out of the hands of the legislative branch and puts it into the executive’s. Chevron also allows for the law to change based on the agency’s current interpretation of it, which is the case in the bumpstock ban matter.

“The rule of lenity is a deeply rooted constitutional principle that ensures legislatures define criminal laws, and that the people have a fair warning of what conduct is prohibited,” said FPC’s Greenlee. “By contrast, the application of Chevron deference in the criminal context would violate several constitutional safeguards. We are cautiously optimistic that the Tenth Circuit will agree that lenity is more appropriate in this case.”


Firearms Policy Coalition ( is a 501(c)4 grassroots nonprofit organization. FPC’s mission is to protect and defend constitutional rights—especially the right to keep and bear arms and free speech—advance individual liberty, and restore freedom.

Firearms Policy Foundation ( is a 501(c)3 grassroots nonprofit organization. FPF’s mission is to defend the Constitution of the United States and the People’s rights, privileges, and immunities deeply rooted in this Nation’s history and tradition, especially the inalienable, fundamental, and individual right to keep and bear arms, through research, education, legal action, and other charitable programs.