I respect your passion on this subject, and frankly I agree with everything you've said in your last reply. The ATF at times have acted precisely like the jack-booted government thugs that Wayne LaPierre so eloquently branded them. Ruby Ridge comes to mind.
However, the law, as passed by congress and signed by the President defines a firearm as "any weapon which is designed to or may readily be converted to expel any projectile by the action of an explosive; or the frame or receiver of any such weapon." (Title 18 USC §232(4)). The statute does not define "frame or receiver" any further. That is left by statute to the authority of the Attorney General to promulgate rules to expand on that definition.
That expansion is found in 27 CFR §479.11 which defines a frame or receiver as "[t]hat part of a firearm which provides housing for the hammer, bolt or breechblock and firing mechanism, and which is usually threaded at its forward portion to receive the barrel." It is this definition of a frame or receiver that the judge had put into question whether a lower receiver of an AR style firearm met. What I don't understand is if the government is in such a panic that this judge's ruling was going to wreak havoc on the ATF's ability to regulate ARs, they simply need to change their definition in the Code of Federal Regulations.
Which is exactly what they did when they attempted to reclassify M855/SS109 "Green Tip" ammunition as "armor piercing handgun ammunition." I know, because I submitted comments in the negative during the public comment period. You can read the aftermath of that comment period here: https://www.atf.gov/news/pr/notice-those-commenting-armor-piercing-ammunition-exemption-framework. The effort was dropped due to overwhelming public comment to the negative.
There was also a proposed regulation reclassifying slide stocks as machine guns instead of firearm parts. Again, I know because I submitted comments in the negative during the public comment period. You can read the response to the comments here: https://www.federalregister.gov/documents/2018/12/26/2018-27763/bump-stock-type-devices#h-106. As you and I are painfully aware, the regulations were ultimately adopted.
Letters of determination as issued by the ATF are not binding law, they are opinions of the ATF. Anyone who disagrees with a letter is free to challenge the letter in court. They essentially describe what the ATF would or would not prosecute. Again, if one wished to challenge one of these letters in court, they are free to do so, but to do so they need to act contrary to the letter, be arrested, and tried in court. Not an avenue that many would voluntarily take just to challenge a ruling, because of the consequences of losing in court.
And unfortunately, it is difficult to challenge these regulations without becoming embroiled in the justice system because of what the courts define as a "lack of standing," which baffles me.
At the time the Northern California office of ATF was gearing up and offered me an opportunity to join them, the news of an wounding of Kenyon Ballew was in the news. He was a 28 year old working man who was wounded by ATF agents who exercised a daytime, knock required warrant, at night around 8:30PM, as Kenyon was finishing his bath, getting ready for bed. The entire warrant was based on an informants information that he knew of someone named Ken who had lots of guns and some grenades who lived in the vicinity. No last name, no exact address, and no further information. When the ruckus started, Kenyon came out of the bedroom in the nude with a replica Walker revolver in his hand, and they shot him in his torso and then they shot him in the head.
There were loads of problems with this ATF raid and warrant.
Later in a Federal Lawsuit, a progressive anti-gun Judge swallowed the ATFs line that Ballew should have known they were coming and were not burglars, despite them avoiding a glass entrance door normally used to enter and leave the apartment, instead electing to use a metal utility door to avoid being identified, and wearing civilian clothing, despite none of them being uniformed officers, and just opened the door to them. . . and that their argument that his having de-militarized and de-activated surplus store souvenir grenades, some made into bookends, was sufficient justification for a raid, because he ALSO was in possession of legal black powder and percussion caps that he COULD, if he had wanted, somehow modified the grenades and restored them to active grenades, just as, in the words of the judge, a person in possession of a bottle, gasoline, and cloth would justify a raid for possession of Molotov Cocktails. As a result the maimed for life Ballew was not entitled to compensation for negligence for being wounded in a misguided and non-justifiable raid. The judge dismissed Ballews suit as the ATF and its agents were immune from such suits.
I did not want to be associated with such a sloppily run organization, which employed keystone Kops agents who did such poor investigations, so I turned them down, despite the good money and benefits.