Consider for discussion, the following...
What fire control parts are in an AR-15 upper?
The bolt carrier, the bolt, the firing pin, the extractor, and the ejector are there, and so is the barrel. So are other parts.
Consider the definition that those parts, bolt, firing pin, etc, are NOT fire control parts. They are the firing parts. There is no "control" there, once activated they do what they do without possibility of interruption or "control".
What controls activation of the firing cycle are OTHER parts, typically in what ever part of the firearm includes the ultimate fire control part, the trigger.
I think the argument can be made that the only actual fire control part is the trigger though I suppose for practicality we should include safeties, as part of the "control" system, when and where they exist.
Since triggers and any other "fire control parts" are typically easily replaceable, rather minor parts, and since they must be housed in something, and without that something, you don't have a functional firearm it made sense to make that the serial# part for legal purposes.
This standard significantly predates the modern modular design of many firearms, we have a situation where traditional definitions are not always as applicable as they once were.
The solution being offered in this case is for the regulatory agency to redefine what they regulate to better adapt it to different designs. The fly in the ointment is that some of us disagree with the expanded definitions.
And, whether or not the agency's redfinitions are within their lawful authority, or if they are usurping the authority of Congress, by using regulation in place of law.
Its a tricksy thing to balance, sometimes..
How is this being imposed without due process, or a change in law?
Did I miss something? How does this just pop up?
As I understand it, due process has been followed, for regulatory changes by the govt. What some are disputing is whether or not it is the province of the ATF or of Congress to make the changes the ATF is making.
How does this "just pop up?" The same way every change in Fed enforcement regulations "pops up". Only a handful of those who would be directly affected pay close attention to what's actually going on, and "calls to arms" to muster public opinion against them are rarely responded to before they are too little, too late.
The issues might be constant front page news but the details of what will be done rarely are, until after they are done.
As I understand it, the law requires the information about proposed changes must be available to the public. It doesn't require it to be easy to find, or understand...