I understand what you're saying, but here's my question: Wouldn't there have to be legislation explicitly sanctioning NoS and allowing any TSA screener to operate them in order to invalidate such a state law? Congress certainly hasn't passed such.

The difference with marijuana that I see is that there are federal laws prohibiting its sale, possession or use. With the NoS, it seems more as though TSA was never told they couldn't do it, so they just did barring a law ruling one way or the other.

Seems more like the case I heard about several years ago (don't remember all the details) where the federal government passed a law that law enforcement officers from any state could carry their weapons in any other state. New York didn't like that, so they passed a law (under which a NJ cop was arrested, if I recall) stating that only officers employed by a NY agency could carry hollow point ammunition. It effectively negates the federal law (since to my understanding that's what most cops carry) but it doesn't expressly conflict with it. I don't know the disposition of that particular case, however.