Really? I don't see any Constitutional authorization for the FDA.
Furthermore, there is solid precedent against your model of how things should work (but then again, precedent is all too often ignored when it is against what one is a proponent of). Consider this; the Federal government needed a Constitutional amendment {the 18th} to regulate a substance (namely alcohol); furthermore, the 18th was repealed in whole by the 21st... so any claim that the government did/does have the authority to regulate drugs (like marijuana, or opiates, etc) based on prohibition is legally null and void.
I never argued that it was Constitutional. I don’t believe that it is, but,that’s a moot point, for the sake of this argument.
All 50 States have laws making cultivation, use and possession illegal. All 50 States use the FDA as their determining authority for medicines. If a State wants to legalize it for medicinal purposes, it stands to reason that it must, first, be approved as such by the only approving authority they recognize, the FDA.