SAN FRANCISCO — Today, attorneys for Firearms Policy Coalition (FPC) filed an important brief with the Ninth Circuit Court of Appeals explaining how the appellate court should apply the Supreme Court’s Second Amendment test for determining the constitutional protection for arms first established in the 2008 D.C. v. Heller ruling and further explained in the 2022 NYSRPA v. Bruen decision.

In its September 5, 2025, order in the case of Knife Rights v. Bonta, the Ninth Circuit requested amicus briefs to address critical questions around the Supreme Court’s use and application of the terms “in common use” and “dangerous and unusual.”

“FPC is interested in this case because it raises fundamental and important questions about the nature and application of the ‘in common use’ test the Supreme Court has established to govern Second Amendment challenges to laws banning a type of weapon,” FPC explained in the brief. “The answers to these questions are of critical importance to FPC’s many members throughout the country, including within this Circuit, who wish to keep and bear common arms for self-defense and other lawful purposes.” Proper application of the Supreme Court’s binding precedents is important to ensuring the full protection of bearable arms by the Second Amendment—a determination that is central to FPC’s ongoing lawsuit challenging California’s unconstitutional ban on so-called “assault weapons,” currently before the Ninth Circuit.

“The questions posed by the Court are fundamental, as they go to the proper understanding and application of the test the Supreme Court has established for determining which ‘Arms’ are protected by the Second Amendment. Fortunately, the importance of the questions is not matched by their difficulty. A plain reading of Heller and Bruen unambiguously resolves several of them,” the brief says.

The brief’s central argument is that the Supreme Court's "in common use" test is the definitive and exclusive constitutional standard for evaluating bans on arms. This test is not a threshold question of textual interpretation, but rather the product of the historical inquiry prescribed by the Supreme Court’s Bruen framework. The burden therefore rests with the government to demonstrate that a weapon is not in common use and is, in fact, "dangerous and unusual." FPC's brief clarifies that these two concepts are inverse and mutually exclusive: if an arm is in common use, it cannot be considered dangerous and unusual, and thus cannot be banned by the government.

To support this brief and dozens of important lawsuits to eliminate gun control laws across the country, join the FPC Grassroots Army at JoinFPC.org.

About Firearms Policy Coalition

Firearms Policy Coalition (FPC) — a 501(c)(4) nonprofit membership organization — exists to create a world of maximal individual liberty, defend constitutional rights, and restore the freedoms guaranteed by the Constitution. FPC pursues these goals through strategic litigation, legal scholarship, amicus briefing, legislative and regulatory advocacy, grassroots activism, education, and outreach. FPC’s legal arm, FPC Law, is the nation’s leading initiative dedicated to restoring the right to keep and bear arms across the United States. To learn more about FPC’s lawsuits and pro–Second Amendment efforts, sign up for FPC news alerts at firearmspolicy.org and follow FPC on X, Instagram, and Facebook.