Except that wasn't the point I was making.
Than, what point ARE you trying to make?
I already explained how the safety regulations of new automobile production are almost completely different than the NFA. I will go further, since you continue your point.
Administrative agencies certainly have power under prescribed law, and can make judgement calls, issue clarifications, and define things within their authority granted by prescribed law. That's not the issue here.
The fact is, the ATF is the one who approved of arm braces and sent letters to manufacturers stating that such items and their use was NOT a loophole or violation of the NFA. When the ATF let these standings hold for as many years as they did, allowing manufacturers to continue to manufacture and sell them by the hundreds of thousands, to hundreds of thousands of customers who bought them on good faith that they were NOT violations or loopholes of the NFA.
When they allowed pistol braces in 2012 they set a precedent that has power, and administrative agencies simply cannot change their minds on a whim about important issues, especially those that involve felony level criminal charges like the NFA carries. When they sent a return letter to Sig on their arm brace in 2015, which is a typical "stock" style arm brace as the ATF now claims, they set a precedent that stood for seven years, and led to many manufacturers making items, and hundreds of thousands of citizens buying them, on clarifications and guidelines SET BY THE ATF THEMSELVES.
When the ATF did so, and did not retract their judgements and guidelines for that many years, with that many sales, and by setting such a long standing PRECEDENT, the ATF de facto ruled that arm braces were not violations of the NFA or loopholes of the NFA.
The point being, administrative agencies and even the courts are expected to follow their own rulings and guidelines, and follow their own precedents. Especially considering the nature of the NFA, and considering it makes potential felonies of those who make small mistakes in following it.
If the arm braces were really a violation of the NFA, the ATF had plenty of time to reject them when they came out, and plenty of time to reject them as they evolved. If it was such an obvious "loophole" of the NFA, why did they send a letter to Sig saying that it was OK for them to make ans ell them? Seven years before arbitrarily changing their mind?
Even if the ATF made a mistake, the fact that they made their rulings with their authority is exactly WHY the pistol braces are no longer fair game for the ATF to rule on any longer.
If you don't like the fact the arm braces are some sort of so called "loophole" of the NFA, than one must place blame on the responsible entity that let them become the issue they are today: the ATF itself.
We have to major reasons to reject the ATF's new ruling: lenity and the fact this carries such serious and extreme crimes with harsh punishments, and more importantly, precedents set by the administrative agencies themselves.
By ruling on arm braces, the ATF sealed itself from making further judgements on arm braces. Their authority under the prescribed law was used, and now is set in hard cement of precedent.
If a king or noble did such, it would be acceptable. They write, judge, and adjudicate their laws. But an administrative agency's ability to administer things is limited, and its ability to change its own rulings is limited.
The case is made, and rightfully so, that if arm braces are to be declared loopholes at this point, it is out of the hands of the ATF because they can't "go back and fix a mistake they made". Not after this much time and precedent. That this is back to the prescribed law to change their NFA status at this point.