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Bump stocks gained national attention after a gunman opened fire from a high-rise hotel room on the 2017 Route 91 Harvest music festival in Las Vegas, killing several dozen people. Several of the rifles found in the gunman’s hotel room were fitted with bump stocks. (AP Photo/John Locher, File)

The 10th Circuit Court of Appeals heard oral arguments on Wednesday in a case challenging the federal government’s ban on bump stocks. The lawsuit involves complex-sounding legal principles like the Chevron doctrine and the rule of lenity, but the plaintiff who has brought the case is seeking an answer to a more simple question: Did the Bureau of Alcohol, Tobacco and Firearms act within its authority when it banned bump stocks, or does a ban require a law change by Congress to be valid?  

Remind me: What are bump stocks, and why are they controversial? 

Bump stocks are attachments for semiautomatic rifles that allow them to function more like automatic weapons. They use gun’s recoil and allow it to slide back and forth quickly, causing it to fire multiple shots in quick succession while the shooter holds their finger on the trigger. 

Bump stocks gained national attention after a gunman opened fire from a high-rise hotel room on the 2017 Route 91 Harvest music festival in Las Vegas, killing several dozen people. Several of the rifles found in the gunman’s hotel room were fitted with bump stocks. 

Although federal legislation introduced after the shooting to ban high-capacity magazines did not gain traction in Congress, the Las Vegas massacre led to the federal ban on bump stocks. 

Possession of new machine guns has been banned since Congress passed the Firearm Owners’ Protection Act in 1986, though machine guns manufactured before the law passed are still legal to possess and transfer. The federal ban on bump stocks came through the Bureau of Alcohol, Tobacco and Firearms, which changed the definition of machine guns to include the devices. 

The ATF’s change took effect in 2019. 

What’s this case in the 10th Circuit about, and how did we get to this point? 

The New Civil Liberties Alliance has sued the Justice Department on behalf of a man named Clark Aposhian, saying the ATF’s ban on bump stocks is unconstitutional because a change to outlaw them would have to go through Congress. He asked a federal judge in Utah to temporarily block the ban from taking effect while his lawsuit moves through the court system. 

Judges tend to grant or decline preliminary injunctions, the legal term for this type of block, based on whether they believe the person (or company) suing is likely to win their case. The federal district judge in Aposhian’s case didn’t think he proved he was likely to win, so she didn’t grant the injunction. 

Aposhian appealed to the 10th Circuit, and a panel of three judges agreed with the lower court decision. But then the 10th Circuit granted Aposhian’s request to rehear the case. On Wednesday, the full court heard oral arguments. This is unusual - three-judge panels are the norm for hearing and deciding cases.

The specific question the court agreed to look at is an indirect way of getting at the ban’s constitutionality. It asks, is it reasonable to interpret the National Firearms Act’s definition of “machine gun” to include bump stocks?

Dave Kopel, the research director for the Independence Institute think tank and an adjunct constitutional law professor at the University of Denver, said the National Firearms Act’s definition of a machine gun to mean a firearm that can fire multiple rounds with “a single function of the trigger” is the wording that, in his belief, gives rise to the need for an act by Congress change that definition because the trigger of a gun fitted with a bump stock moves back and forth with the rest of the weapon.

“So I've argued, it's got to be a change done by Congress to change the statute because the statute says, 'a single function of the trigger,'” said Kopel, who would support legislation that includes bump stocks in the definition of machine gun conversion kits, which are also banned by the National Firearms Act. “And as described, the bump stock has multiple operating functions of the trigger.”

During the arguments presented by Brad Hinshelwood, the attorney representing the Department of Justice, the judges zeroed in on that difference. Judge Jerome Holmes called the function of bump stocks “a single pull of the trigger-plus.” 

Hinshelwood argued other courts that have interpreted the meaning of a single trigger “function” have interpreted have looked at the action taken by the shooter to initiate a firing sequence. He said the ATF’s rule defines a single function as a single trigger “pull” and comparable actions. 

“There’s a whole range of possible trigger devices and ways you can start a firing sequence, and in this instance all you have to do is pull the trigger one time, and then that will initiate the cycle that functions automatically,” he said.

So will the judges on the 10th Circuit decide whether to keep the ATF’s rule in place?

Not necessarily. The judges can take a few different approaches to deciding the case that are less direct than upholding or striking down the bump stock ban. They could make a decision about the preliminary injunction denied by the district court.

Chris Jackson, a partner at Holland & Hart, said a decision about the injunction would be a likely reliable indication of how the court would rule on the ATF’s ban itself, because judges look at how likely they think the requestor is to succeed on the merits of their case as a significant factor in decisions about injunctions.

“They can't say, “This is what we're going to rule on.’ But when the entire court rules, and it says, “We think you're very likely or very not likely to succeed on the merits,’ that's a pretty clear indication of what's going to happen,” he said.

The case also puts two legal principles at odds with each other, a conflict that sets up another framing for a decision. One is called the Chevron doctrine, which directs courts to give deference to government agencies’ interpretations of laws if they are reasonable. The other is the rule of lenity, a principle in criminal law. It says an ambiguous law should be interpreted in favor of a defendant. The rule is relevant here because the ATF’s ban makes possession of bump stocks a felony, including those purchased before the rule went into effect.

“In this case, you kind of have an overlap of those two issues, because the ATF's regulation makes it illegal to own a bump stock,” Jackson said. “On the one hand, Chevron deference gives the ATF some deference: If it's a reasonable interpretation, we're going to allow you to make it illegal. But then the rule of lenity says if there's an ambiguity, you're supposed to pick the interpretation that favors a criminal defendant, which means like you should not make bump stocks illegal. And so I think one of the issues the 10th Circuit is interested in is, how do you reconcile that?”

“We can either apply deference, or we can apply lenity, and lenity has to take precedence because of its constitutional roots,” said Caleb Kruckenberg, the NCLA attorney arguing on behalf of Aposhian, to the judges during his argument time. 

Jackson said he believes the 10th Circuit probably won’t make a ruling that directly decides the fate of the bump stock ban, and more likely will decide based on the injunction or the tension between the Chevron doctrine and rule of lenity. But of those possible rulings, he said, the 10th Circuit’s decision is anyone’s guess. 

“There's no way really to know if they're going to do that first thing or that second thing,” he said.