O’Connor first granted that partial injunction in favor of Tactical Machining last September, and added Blackhawk Manufacturing Group to the injunction back in November. In that respect, it wasn’t a huge surprise to see O’Connor add Polymer80 to the list of companies protected from the rule’s enforcement, but his ruling is still a very welcome development.

In his ruling, O’Connor said the ATF has likely overstepped its mandated authority by treating unfinished frames and receivers as if they were already firearms governed by the Gun Control Act of 1968. The judge noted that while Congress declined to define frames and receivers in the GCA, it also didn’t include partially assembled frames and receivers in its definition of “firearm”.

The Final Rule’s redefinition of “frame or receiver” conflicts with the statute’s plain meaning. The definition of “firearm” in the Gun Control Act does not cover all firearm parts. It covers specifically “the frame or receiver of any such weapon” that Congress defined as a firearm. 18 U.S.C. § 921(a)(3)(B). That which may become a receiver is not itself a receiver. Congress could have included firearm parts that “may readily be converted” to frames or receivers, as it did with “weapons” that “may readily be converted” to fire a projectile. But it omitted that language when talking about frames and receivers. “[W]hen Congress includes particular language in one section of a statute but omits it in another section of the same Act, it is generally presumed that Congress acts intentionally and purposely in the disparate inclusion or exclusion.” Collins v. Yellen, 141 S. Ct. 1761, 1782 (2021) (citation and internal quotation marks omitted). Likewise, when Congress uses a phrase in one part of a definition and excludes that phrase from another part of the very same definition, courts should give effect to Congress’s deliberate exclusion.

Congress excluded other adjectives that ATF adds to its definition. The Final Rule covers “disassembled” and “nonfunctional” frames and receivers. 27 C.F.R. § 478.12(c). Congress’s definition does not. Again, compare the language in Congress’s primary definition of “firearm” to its secondary definition covering frames and receivers. The primary definition of “firearm” includes any “weapon” that “is designed to” fire a projectile. 18 U.S.C. § 921(a)(3)(A). That language covers disassembled, nonfunctional, and antique firearms because they are “designed” to fire projectiles even if they are practically unable to do so. But Congress wanted to exclude antiques, so it explicitly said the “term does not include an antique firearm,” once again demonstrating awareness of the scope of the language it chose. Id. § 921(a)(3). In contrast, Congress did not choose to cover firearm parts that are “designed” to be frames or receivers— that is, incomplete, nonfunctional frames or receivers. “That omission is telling,” particularly when Congress used that more expansive terminology in the same definition. Collins, 141 S. Ct. at 1782.

ATF’s new definition of “frame or receiver” in 27 C.F.R. § 478.12(c) is facially unlawful. By comparison, the Final Rule includes definitions of “frame” and “receiver” in § 478.12(a) that appear to be consistent with the statute. This further highlights that the Final Rule’s expansion of authority in § 478.12(c) to firearm parts that are not yet frames or receivers goes beyond Congress’s definition. In other words, § 478.12(a) describes the full scope of frames and receivers that are consistent with the statutory scheme. ATF’s expansion in § 478.12(c), on the other hand, covers additional parts that are “designed to or may readily be completed, assembled, restored, or otherwise converted to function as a frame or receiver.” 27 C.F.R. § 478.12(c). But Congress intentionally omitted that language from the definition. Section 478.12(c) is thus facially unlawful because it describes only parts that Congress intentionally excluded from its definition of “firearm.” It is purely an expansion of authority beyond the statutory language. That the firearm part is “designed” to be or may one day become a frame or receiver does not change the fact that, in that moment, it is not “the frame or receiver of any such weapon.” 18 U.S.C. § 921(a)(3)(B).

O’Connor was unpersuaded by the DOJ’s argument to the contrary, and pointed out that the rule over unfinished frames and receivers even includes a new definition of “firearm” that contradicts the definition provided by Congress back in the 1960s.

Under the Final Rule, “[t]he term shall include a weapon parts kit that is designed to or may readily be completed, assembled, restored, or otherwise converted to expel a projectile by the action of an explosive.” 27 C.F.R. § 478.11 (definition of “firearm”). That language conflicts with the statute’s definition of “firearm.” Despite Defendants’ arguments to the contrary, ATF has no general authority to regulate weapon parts. But the Final Rule grants ATF that general authority by copying language used throughout the statutory definition. It takes phrases like “designed to” and “may readily be converted” and “assembled” from various places in the statute, cobbling them together to form ATF’s own definition of “firearm.” Those terms may add a patina of credibility to the drafting, but they tarnish Congress’s carefully crafted definition. More importantly, they unlawfully expand ATF’s authority beyond the boundaries set by the Act.

One of the great things about O’Connor’s ruling is that it cuts through all of the Biden administration’s obfuscations of current statute and gets to the heart of the matter: Congress has granted authority to the ATF to regulate “firearms”, not gun parts in general, things that could become firearms at some point, or gun-making kits.

Congress could have described a firearm as “any combination of parts” that would produce a weapon that could fire a projectile. It used that language elsewhere in the definition. Id. § 921(a)(4)(C). Congress could have described a firearm as any part “designed” to be part of a weapon. It used that language too. Id. § 921(a)(3)(A), (a)(4)(C). Congress could have described a firearm as a set of parts that “may be readily assembled” into a weapon, as it did for “destructive device.” Id. § 921(a)(4)(C). Congress could have written all those things, and the very definition of “firearm” demonstrates that Congress knew the words that would accomplish those ends. But Congress did not regulate firearm parts as such, let alone parts kits that are “designed to or may readily be completed, assembled, restored, or otherwise converted to expel a projectile by the action of an explosive.” 27 C.F.R. § 478.11.

If Congress wants to revisit the Gun Control Act of 1968, it could choose to do so. But congressional inaction isn’t an excuse or opportunity for the ATF or DOJ to start creating laws on their own, which is exactly what the ATF has done with its re-definition of “firearm.” O’Connor’s decision to grant an injunction against the rule as it applies to Polymer80 and its customers isn’t just good news for gun owners. It’s the right call for anyone concerned about bureaucratic overreach and executive branch abuses of authority.