This is not the case, legally. I'll try to be general with this, and not try to bring in constitutionality.

Look at the recent quagmire regarding work rule requirements in California about having breaks. Held to be legal, constitutional, and binding all the way up the judicial food chain, and is resulting in multiple airlines reconsidering having California bases.

Look also at a lot of California, Colorado, and Illinois requirements for sick leave, harassment training, and parental leave. Also found to be binding for the airline, or at least crews based in that state.

It's about what is more restrictive. Federal law can supersede state law and vice versa, but only in that circumstance. And a CBA can't override/waive state OR federal law, despite what gets ratified and/or signed.