The odds of the Supreme Court weighing in on the Trump administration’s move to ban bump stocks have improved after the Fifth Circuit Court of Appeals on Friday declared that the ban was unlawfully put in place back in 2018. The decision means there’s now a split among the various appellate courts, and that in turn makes it more likely that SCOTUS will take up one or more of the challenges that have been slowly making their way through the court system.

In this particular case, known as Cargill v. Garland, an en banc panel on the Fifth Circuit agreed 13-3 with the argument that the ATF’s sudden declaration that bump stocks were “machine guns” not only reversed years of settled policy, but completely ignored the meaning of the phrase “machine gun” as defined by the Gun Control Act and National Firearms Act.

A plain reading of the statutory language, paired with close consideration of the mechanics of a semi-automatic firearm, reveals that a bump stock is excluded from the technical definition of “machinegun” set forth in the Gun Control Act and National Firearms Act.

But even if that conclusion were incorrect, the rule of lenity would still require us to interpret the statute against imposing criminal liability. A rich legal tradition supports the “well known rule” that “penal laws are to be construed strictly.” United States v. Wiltberger, 18 U.S. (5 Wheat.) 76, 94–95 (1820). As Chief Justice Marshall explained long ago, the rule “is founded on the tenderness of the law for the rights of individuals; and on the plain principle that the power of punishment is vested in the legislative, not in the judicial department. It is the legislature, not the Court, which is to define a crime, and ordain its punishment.” Id. at 95.

The Government’s regulation violates these principles. As an initial matter, it purports to allow ATF—rather than Congress—to set forth the scope of criminal prohibitions. Indeed, the Government would outlaw bump stocks by administrative fiat even though the very same agency routinely interpreted the ban on machineguns as not applying to the type of bump stocks at issue here. Nor can we say that the statutory definition unambiguously supports the Government’s interpretation. As noted above, we conclude that it unambiguously does not. But even if we are wrong, the statute is at least ambiguous in this regard. And if the statute is ambiguous, Congress must cure that ambiguity, not the federal courts.

The definition of “machinegun” as set forth in the National Firearms Act and Gun Control Act does not apply to bump stocks. And if there were any doubt as to this conclusion, we conclude that the statutory definition is ambiguous, at the very least. The rule of lenity therefore compels us to construe the statute in Cargill’s favor. Either way, we must REVERSE.

With the Sixth, Tenth, and D.C. Circuit appeals courts all previously upholding the ATF’s bump stock rule this case now appears ripe for Supreme Court review, and the implications of any SCOTUS decision could have an impact on Joe Biden’s attempts to impose further restrictions on firearms through ATF fiat; including the already enacted (and challenged) rules on unfinished frames and receivers, the pending rule on pistol stabilizing braces, and the gun control lobby’s desired reclassification of many common semi-automatic firearms as machine guns as well. As the Fifth Circuit makes clear, neither the Gun Control Act nor the National Firearms Act bestow the ATF with the power or authority to craft new law, but that is in essence what the agency has done by interpreting and redefining terms within statute so broadly that they end up being rewritten entirely.

Under the definition provided of a machine gun in federal statute, a firearm must shoot “automatically more than one shot… by a single function of a trigger.” Non-mechanical bump stocks, however, don’t allow for multiple rounds to be fired with one pull of the trigger. Instead, a bump stock helps to assist in a more rapid pull of the trigger, but it doesn’t change the actual function of the firearm. As the Fifth Circuit notes, if Congress wanted to change that definition or simply ban bump stocks via legislation that would be one thing, but the agency doesn’t possess the power to rewrite the laws all by itself.

We reiterate that a shooter can bump fire an ordinary semi-automatic rifle even without a bump stock. But nobody, not even the Government, contends that semi-automatic rifles are machineguns. That concession damns the Government’s position. As Cargill recognizes, if ordinary bump firing constituted automatic fire, the Final Rule would “convert a semiautomatic weapon into a machinegun simply by how a marksman used the weapon.” That absurd result reveals the flaw in the Government’s line of reasoning.

In addition to implying absurd results, the Government’s position is quite telling. It would allow the use of semi-automatic rifles, which can bump fire, but prohibit the use of non-mechanical bump stocks, even though there is no mechanical difference between the two forms of gunfire. Rather, the meaningful difference is that, with a non-mechanical bump stock, bump firing is easier and can occur at a faster rate. That is a distinction Congress certainly could have addressed in the National Firearms Act and Gun Control Act. But Congress did not prohibit machineguns according to how quickly they fire. It prohibited machineguns according to the way that they fire. And semiautomatic weapons do not fire “automatically,” even when equipped with a non-mechanical bump stock.

It’s a solid opinion, and I’d encourage you to read the whole thing when you get a chance. Congratulations to Michael Cargill, the New Civil Liberties Alliance, and all of the groups (Second Amendment-focused and otherwise) who submitted amicus briefs in support of Cargill’s challenge, which will hopefully soon be taken up the Supreme Court now that there’s solid disagreement in the lower courts about the validity and legality of the administrative ban.