CNN reports on today’s Supreme Court oral arguments:

Several conservative Supreme Court justices indicated Wednesday they are concerned with the federal ban on bump stocks, a device that allows semi-automatic weapons to fire more like a machine gun.

Justice Brett Kavanaugh said he was worried about Americans being prosecuted under a ban they aren’t aware of. And Justice Amy Coney Barrett said that while she was “intuitively” concerned about the bump stock devices, she questioned why the issue wouldn’t be better handled by Congress.

That was a theme that the justices returned to repeatedly, underscoring a push by the court’s conservatives to limit the power of federal agencies in recent years.

Forgive me for being a broken record on this topic, but this framing drives me as crazy in this instance as it does everywhere else. The question in this case is statutory. That “the justices returned to” that question repeatedly is not some curious foible of this particular “conservative” majority, but the inevitable reflection of the task that the justices have been asked to perform. What we have here is a dispute between a federal agency (the ATF), which says it is legally permitted to ban bump stocks, and a plaintiff (a Texas gun-shop owner), who insists that the ATF is wrong. The role of the Supreme Court is not to decide, in some abstract sense, whether the federal bureaucracy is too big or too small — or, as CNN implies, “to limit the power of federal agencies” per se — but to adjudicate whether, in this particular area, the federal government has been granted the power it claims. If, as the plaintiffs insist, the ATF’s behavior is not warranted by the law that Congress already passed, then it is not merely the case that the issue would be “better handled by Congress,” it is the case that the issue must be handled by Congress, because Congress has not yet handled it. If the plaintiffs are wrong, then they are wrong because the issue was already handled by Congress, not because it is unnecessary for Congress to act. On this, Article I is extremely clear.

At stake here is whether the Trump administration’s 2018 redefinition of the term “machinegun” is compatible with the terms of the 1934 National Firearms Act. As such, most of today’s discussion was highly technical, with the vast majority of the back-and-forths revolving around the meaning and application of one term from that statute: “single function of the trigger.” The government claims that the NFA’s definition of “machinegun” can be used to cover bump stocks, because bump stocks have the effect of making semi-automatic firearms more like automatic firearms. The plaintiffs — along with both the Fifth Circuit and Sixth Circuit, which both found in their favor — say that this is untrue per se, and that, even if the law were to be deemed ambiguous, the rule of lenity would require a ruling in their favor. While other topics came up from time to time, the debate kept returning to the text — not because Amy Coney Barrett or the “conservatives” have some secret agenda, but because this is a textual case.

Ultimately, the outcome will be determined by how textualist the Court wishes to be. As is her wont, Elena Kagan kept asking the plaintiffs’ attorney, Jonathan F. Mitchell, what Congress had been trying to achieve with this law, and, as was his duty, Mitchell kept replying that what mattered more was what Congress actually wrote down. If a majority of the justices agree with Mitchell, the case will be an easy one to resolve and the plaintiffs will win going away. As Robert VerBruggen has noted repeatedly, “the statute governing ‘machine guns’ defines the term in a way that simply doesn’t describe how a bump stock functions,” and, as such, the executive branch “has no authority to rewrite” the law to accomodate them. Whether it will be given that authority by the Court nevertheless is a separate question — and, at this point, anyone’s guess.