Unmarked no-fly zones at unannounced times and locations are a remarkable innovation. Hopefully they will tell you when and where you shouldn't have been when they charge you for it, but that may be classified.
For whatever it’s worth, I don’t think these rules would stand under the APA. Which means any criminal convictions would be thrown out.
Heck if they do tell you, ICE swaps plates and tries to hide in various ways.
The evidence could be just some regular looking vehicle you can't find anything about and it's just "trust me bro those were feds" and you're out of luck.
Up next, secret interpretations of laws to do things with zero accountability or public overaight. Oh wait we already have that.
Before you know it, they'll be detaining people without legal representation, shipping them to overseas black sites, and murdering citizens in the street. Oh, wait that's been the entirety of this treasonous administration.
Ambiguous laws (which in this case are by definition impossible to comply with) which are capriciously enforced are a hallmark of authoritarian and fascist regimes. Sadly ironic, the US government used to highlight this fact:
"Authoritarian regimes’ unclear laws make anyone a suspect" - https://ge.usembassy.gov/authoritarian-regimes-unclear-laws-...