The ban on bump stocks was implemented using the Firearms’ Owners Protection Act of 1986. Which was signed into law by Reagan (funny how a failed assassination will change things).

The text at issue is

SEC. 109. AMENDMENT OF NATIONAL FIREARMS ACT. (a) Section 58450)) of the National Firearms Act (26 U.S.C. 5845(b)) is amended by striking out “any combination of parts designed and intended for use in converting a weapon into a machinegun,” and inserting in lieu thereof “any part designed and intended solely and exclusively, or combination of parts designed and intended, for use in converting a weapon into a machinegun,”

IMO the majority in this decision is choosing to blatantly ignore the text of the act which was clearly chosen to future-proof for any advancement which would result in an effortless high rate of fire such as bump stock and super safety. Instead they are insisting that Congress must amend the law to include specific parts which of course is a losing battle as there will always be a new part that achieves an effortless high rate of fire.

Now where one could argue that this ruling is correct is the accepted definition of a machinegun requires a single trigger action.

26 U.S.C. § 5845(b)

Any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot without manual reloading, by a single function of the trigger

Personally I think the laws should be amended to define weapons and munitions by their result (high or continuous rate of fire) instead of their form or function. As it stands, someone could create a weapon that simply fires continuously but does not resemble a gun in any other way. Would such a weapon be a machinegun if it doesn’t even have a trigger?

I think the dissenting opinion was more inline with the intent of FOPA.