Seeing so many posts about people talking about the ATF "Banning Pistol Braces" and now how "AG Marek Garland signed it." I'll break down why you shouldn't worry nor why you have to comply.
What can the ATF CAN DO?(Skipping the Alcohol and Tobacco)
1. Legally, the ATF has the authority to "Investigate & Prevent gun laws from being violated".
2. Propose rule changes as well as the definitions of certain things. The proposal is submitted to legislators.
3. Has authority over what FFLs can and can't sell, depending on state and federal laws. Laws that are created and passed by legislators.
4. Obtain a search warrant, if there is evidence to suspect an FFL or gun owner is in possession of an illegal firearm or, selling illegal firearms.
5. Has authority to arrest said person found in possession or sale of illegal firearms.
6. Has the authority to revoke an FFL or Gun Manufacturer license if evidence is shown they are committing crimes.
7. Enforce the NFA(National Firearms Act), and anything in it that has been passed by legislators as "Illegal".
What the ATF CAN'T DO?(Skipping the Alcohol and Tobacco)
1. Create gun laws. Laws can only be created by Local, County, State and Federal Legislators. Law Enforcement agencies can't make laws, period.
2. Enter or Search your house, business or property without a Search Warrant signed by a judge.
3. Detain, Arrest or Charge you for owning something that hasn't been deemed illegal by Local, County, State or Federal Legislators.
4. Enforce "Rules" and "Definitions" unless they become law through Legislation.
5. Force Local, County, State or Federal Law Enforcement Agencies to enforce "New Rules & Definitions" since they are not laws passed by Legislators.
6. Add new items to the NFA(National Firearms Act) without Legislators passing a bill.
To put it simple, the ATF DOESN'T have the authority/power to make new laws & regulations, only Legislators have the power to create new laws. Federal, State, County and Local courts have the power to deem those laws 'Constitutional' or 'Unconstitutional'. Law Enforcement has the power only to enforce laws. The ATF is apart of the DOJ(Department of Justice) and is a Law Enforcement Agency, which means, they can only enforce laws created by Legislators and deemed 'Constitutional' by the courts. The can purpose any new rules and definitions they want, and change them in their heads, but it doesn't make it law, which means you don't have to comply with it.
If law enforcement, prosecutors or the ATF try and enforce these, the case doesn't stand a chance in court, since no law has been broken. The only thing they can do, is try and get you to commit to a Crime. For Example, if they ask you if you own a Rare Breeds Trigger, Solevent Trap, or Pistol Brace attached to your AR, and you lie about it and they find or have evidence that you do. That's a crime, lying to law enforcement, in this case a federal law enforcement agent. Now since you're a felon for getting caught lying, they can confiscate your firearms and parts. The other way they can charge you with a crime, for example having a Rare Breeds Trigger, or Solevent Trap, or Pistol Brace, is if you confess or state your intent is to use a RBT to turn it into a machine gun(Which is impossible), a Solevent Trap to use as a non-NFA stamped Suppressor, or use a Pistol Brace to make an SBR. Since possession of a post-1986 machine gun is illegal, since a non-NFA suppressor is illegal and since a non-NFA SBR is illegal, they can and will arrest you. It's their tricks, since they can't arrest you for possession of these items because these items aren't illegal, they will try and make you confess to intented to use said items to make an illegal or non-registered NFA firearm, or part.
What can you do?
1. Don't answer the door if they come a knocking. You do not have to answer the door to anyone.
2. Don't let them in. Again, you have the right to refuse them entry unless they have a warrant, signed by a judge.
3. Just don't talk to them. You don't have to talk to them at all. If you don't talk, they can't trick you. Most arrests are by people self snitching on themselves. So do yourself a favor and don't talk, and if you are somehow charged with something, still don't talk and get a lawyer.
What's the take away? ATF new "Rules & Definitions" are not laws. The ATF uses fear to make people comply and the ATF will use tricks to make you confess to an actual crime, if you decide to talk to them. The ATF can't make laws, only Legislators can.
Legislative—Makes laws (Congress, comprised of the House of Representatives and Senate) Executive—Carries out laws (president, vice president, Cabinet, most federal agencies) Judicial—Evaluates laws (Supreme Court and other courts) -USA.GOV
Copied from someone with more understanding of the ATF than I do.
Editing to add this: 18 U.S.C § 926 prohibits the ATF from creating and/or maintaining a firearm registry.