There are whole laws that are classified and cannot be discussed in open court. Ignorance of the law is no defense when you are charged with violating a law and that’s still true in the USA even if the law is classified and you are not authorized to know what it says.
Check out Gilmore v Gonzales for an example: https://en.wikipedia.org/wiki/Gilmore_v._Gonzales
Airlines can refuse to carry people whose name starts with a vowel, if they want to. That's a principle of free business.
Is there more to this than the Wikipedia article says?
While it does say:
> Gilmore also complained about being subject to "secret law", when the airlines and government refused to show the directive under which they were requesting ID.
nowhere does the article say the courts commented on the complaint, let alone ruled on it.
Nor does the article say anything about "Ignorance of the law is no defense when you are charged with violating a law". The reason given was instead:
> there was no constitutional violation because air passengers could still travel without identification if they instead underwent the more stringent "secondary screening" search.
I'm not saying your wrong, just that the article you offered as evidence doesn't go as far as your claims.