Originally Posted by rickair7777

The regulator can change it after, like you said, some due process including public commentary. Unless an existing federal LAW proscribes the change in question.

Congress can always pass a law which would always supersede bureaucratic regulations and process (assuming POTUS signs it). No particular due process required, other than normal legislative process. Although some analysis would probably get done by somebody, staffers or lobbyists, and used as supporting material during the committee/ congressional debates. Good chance legislators would ask for the regulator (FAA) to weigh in with their opinion and data. But ultimately congress and laws supersede bureaucrats and regulations, however it plays out. IIRC that's how got the 1500 hour/ATP rule.

Current FARs have, in some cases, matching federal law. IIRC examples are PEDs, alcohol, falsification of FAA forms and there are others. Typical reason is to put criminal teeth behind certain regs.

There are many other FARs which have no matching federal law, and are only subject to regulatory/admin law/civil enforcement. Example would be landing currency, there's no federal criminal penalty if you're out of currency so not going to jail for that.