The Constitution provides foundational rules for the operation of our government. Congress writes the laws. The Executive Branch enforces them. And the Judiciary independently interprets them. But this case threatens to consolidate all three functions in a single administrative agency—the ATF—and to contravene both the laws written by Congress and prior judicial interpretations of those laws. Worse, the ATF has rewritten a criminal statute and is prepared to prosecute hundreds of thousands of law-abiding citizens who relied on prior approval of their ownership of “bump stocks” from that same agency.

This result subverts the constitutional order and could only arise from an unwarranted extension of an already questionable constitutional doctrine: Chevron deference. As several justices on the Supreme Court have noted, the Chevron doctrine is, to say the least, constitutionally problematic. Among other things, the doctrine requires courts to abandon their duty of independent judgment, and it violates due process by requiring courts to favor one litigant—the government—over another. As a practical matter, Chevron creates a perverse incentive for Congress and the courts to shirk their constitutional responsibilities and turn difficult legislative or interpretive decisions over to administrative agencies. In amici’s view, Chevron is itself unconstitutional.

While NCLA recognizes that the constitutional validity of the Chevron doctrine is not a matter for this Court to resolve in opposition to the Supreme Court, the Supreme Court’s reliance on Chevron has waned over the last half a decade. All courts should thus be mindful of the danger Chevron poses to due process, judicial independence and the separation of powers. Only then can they be sure they are discharging their duty to say what the law is, not what the law should be. Only then can they be sure, when the government is a party, that they are not denying due process to the other party. And only then, in controversial cases such as this one, can they be sure that, whatever the merits of banning bump stocks, the decision remains with Congress—not the ATF, not the President, and not the courts.

Congress has not banned bump stocks. It has banned machineguns, but the statutory definition of “machinegun” does not include bump stocks—a fact which the ATF understood up until bump stocks became a matter of great public concern. In upholding the Final Rule, the district court misapplied Chevron step one in two ways. First, it improperly concluded that the statute is ambiguous because Congress did not define the terms “automatically” and “single function of the trigger” in the definition of “machinegun.” Second, it conflated Chevron step one with step two, by choosing the ATF’s rewrite of the statute because it is allegedly “reasonable.” But, as a number of courts have held, the statutory definition of “machinegun” is not ambiguous, so it was improper for the district court to consider the reasonableness of the ATF’s new definition at all.

But even if the statute were ambiguous, the district court still improperly ignored the impact of the rule of lenity. Finally, without Chevron deference, the ATF’s interpretation of the statute fails because it clearly is not the “best view” of the statutory language.

This Court must now remedy those errors. In a case such as this, where accepting the agency’s construction will result in the prosecution of otherwise innocent Americans, this Court cannot abdicate its independent constitutional responsibility to say what the law is.

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