A bump fire stock that attaches to a semi-automatic rifle to increase the firing rate at Good Guys Gun Shop in Orem, Utah, October 4, 2017. (George Frey/Reuters)

A federal judge has allowed the ban to go forward, refusing to grant a preliminary injunction in one of the cases challenging it. As you may recall, a bump stock is a device that allows an ordinary semiautomatic weapon to fire rapidly like a machine gun, and the Trump administration’s Bureau of Alcohol, Tobacco, Firearms and Explosives decided to ban such devices by administrative fiat last year when Congress failed to act.


On the fundamental issue here — whether the ban contradicts the law it purports to “reinterpret” — the judge writes that the challenge is “unlikely to succeed on the merits.” She argues that (A) Supreme Court precedent requires great deference to executive agencies’ interpretations of the law and (B) the law at issue here is ambiguous enough that the administration’s interpretation is fair game. She’s right about (A), though many argue that the Supreme Court’s approach is wrong and courts should more aggressively police agencies’ efforts to expand the authorities they’ve been given. But for reasons I’ve laid out several times before, even if we have to give the administration a lot of leeway, I disagree with her on (B).

A weapon is a “machinegun” under federal law if it can automatically fire more than one round “by a single function of the trigger.” Bump stocks do not meet this definition. In fact, they don’t affect the functioning of the trigger, or the relationship between the trigger’s movements and the number of rounds discharged, at all. They’re stocks, the part of the gun that meets the shooter’s shoulder, and they help the user pull the trigger repeatedly and quickly. Essentially, the user holds his trigger finger steady while pulling the gun forward with his other hand, and the recoil of the gun makes the trigger bounce back and forth against the trigger finger. The trigger still functions one time for every shot fired.


As the ruling puts it, the Trump administration tries to sidestep this fact by interpreting “function of the trigger” to mean “pull of the trigger from the perspective of the shooter” — i.e., a separate, deliberate manipulation of the trigger by a human. Which is a far cry from a “single function of” a mechanical device.

In addition, since owners of legally purchased bump stocks need to turn them in or destroy them without compensation, the plaintiffs in the case argue the ban violates the Constitution’s takings clause. On this, the judge says that even if the plaintiffs are correct, “future compensation” is the appropriate remedy and thus no injunction halting the ban is called for.


From the beginning I’ve been saying that Congress should address bump stocks through a new piece of legislation, rather than counting on the executive branch to twist the language of a law passed in the 1930s, and on the courts to play along. I still think that’s the best course, even if courts are playing along so far.

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