Firearms Owners Protection Act (FOPA)-Federal Law 18 U.S.C. 926(a):
No such rule or regulation prescribed [by the Attorney General] after the date of the enactment of the Firearms Owners Protection Act may require that records required to be maintained under this chapter or any portion of the contents of such records, be recorded at or transferred to a facility owned, managed, or controlled by the United States or any State or any political subdivision thereof, nor that any system of registration of firearms, firearms owners, or firearms transactions or disposition be established. Nothing in this section expands or restricts the Secretary's authority to inquire into the disposition of any firearm in the course of a criminal investigation.
Since the Firearms Owners Protection Act is an act of Congress, another act of Congress can nullify it.
Any law may be amended by another new law. In fact, if you were to read how most legislation is written, it merely uses the previous law as a template and makes language changes.
And just when have government ever followed laws? There are no consequences to government employees who break the law.