In “ghost gun” case, Justice Kavanaugh suggests due process defense “based on lack of fair notice” for potential federal firearm crimes
The Supreme Court this morning decided the so-called “ghost gun” case, Bondi v. Vanderstok, No. 23-852 (March 26, 2025) (available here), which addressed the lawfulnees of an ATF rule interpreting the Gun Control Act of 1968 to cover weapon parts kits. By a 7-2 vote, the Court rules that the “GCA embraces, and thus permits ATF to regulate, some weapon parts kits and unfinished frames or receivers.” Some small interesting elements for criminal law fans include Justice Gorsuch, who wrote the opinion for the majority, disposing of a “rule of lenity” argument in just a sentence. Justice Thomas, who authored a lengthy dissent, states at the end that he “would apply the rule of lenity here.”
As the title of this post reveleas, the criminal justice item that caught my eye in Vanderstok was a short concurrence by Justice Kavanaugh. Here is his five-paragraph concurrence in full with my empahsis added toward the end:
I join the Court’s opinion in full. I add this concurrence to briefly address mens rea issues with respect to ATF’s 2022 rule.
Under ATF’s rule, an individual or business acting in good faith might nonetheless have substantial difficulty determining when weapon parts kits or unfinished frames or receivers qualify as firearms — and thereby become subject to the Gun Control Act’s licensing, recordkeeping, serialization, and background-check requirements. Some weapon parts kits and unfinished frames or receivers may qualify as firearms, and others may not. See ante, at 13, 21. The line is not entirely clear. Despite the vagueness of the line, the penalties for violations are significant and can include fines and imprisonment. See 18 U.S.C. § 924.
But importantly, under the Gun Control Act, someone can be penalized for violating the licensing, recordkeeping, or serialization requirements only if he does so “willfully.” § 924(a)(1)(D). To prove “willfulness,” the Government must demonstrate that an individual knew that his conduct was unlawful, not merely that he knew the facts that made his conduct unlawful. Bryan v. United States, 524 U.S. 184, 191–196 (1998). Therefore, with respect to ATF’s rule, the “willfulness” requirement should help prevent the Government from unfairly penalizing an individual who is not aware that his conduct violates the law.
As to background-check violations, by contrast, the statute penalizes violations committed “knowingly.” §§ 922(t), 924(a)(5). The “knowingly” mens rea requires “proof of knowledge of the facts that constitute the offense.” Id., at 193. Unlike the “willfully” mens rea, it generally does not require knowledge that the conduct was unlawful. See id., at 192–193. That lesser “knowingly” mens rea requirement could therefore create concerns about fair notice, at least in certain cases. See Wooden v. United States, 595 U.S. 360, 379 (2022) (KAVANAUGH, J., concurring).
That said, at oral argument, the Government represented that it would “likely” decline to “charge someone” for a background-check violation in the “kind of situation” where the individual was not aware that he was violating the law. Tr. of Oral Arg. 46–47. As the Government seemed to recognize, if the Government were to charge a backgroundcheck violation against an individual who was unaware that he was violating the law, that defendant might have a due process argument based on lack of fair notice. I expect that the Government will seek to avoid that potential fair-notice problem by adhering to its oral-argument representation that it would likely decline to bring charges in those circumstances.
Though I am not an expert on all jurisprudence supporting a “due process [criminal defense] based on lack of fair notice,” I read Justice Kavanuagh as pushing existing jurisprudence here. Notably, he just says a defendant “might” have a “due process argument,” and he does not cite any caselaw in which such an argument was developed. Moreover, I wonder how such a claim would get litigated. What if an individual said he was unsure if a gun part was subject to the ATF rule because he decided not to research the matter?
Generally speaking, the Supreme Court and lower courts have tended to treat mens rea issues as matters of statutory interpretation, not as matters of constitutional dispute. But Justice Kavanaugh, who often raises mens rea issues in a variety of settings, once again highlights his particular concerns with mental states and criminal enforcement. And it seems, based on the sentence highighted above, that his concerns sometimes are of a constitutional dimension.