That language just lets aviation entities off the hook as far as responsibility for pax compliance.

But that does not make weed/THC legal anywhere in the US, it's technically not under federal law.

When states legalize the stuff, all they're doing is promising that the STATE won't penalize you or arrest you on behalf of the feds. That does NOT protect you from the fed itself, even in a weed "legal" state. Especially if you set foot on federal property/jurisdiction, such as a military base or courthouse.

Also you could have an issue if you divert to another state or even country. If you do, you need to toss that stuff in the trash at the first opportunity, don't try to bring it back through security in a place like WY, ID, etc. Although even some conservative states are shifting to a traffic-ticket model for personal use quantities, instead of jail.

Local/state police usually have an airport presence and I've seen drug dogs making the rounds in terminals recently. Yes that's legal, and no they don't need probable cause other than the dog alerting.

Of course if you carry enough to trigger whatever the local or federal threshold is for commercial possession, that's a whole different story, feds and many states will throw the book at you.