I'm not accounting for State laws; which may in fact be stricter. I'm talking about Federal Laws which might not explicitly forbid such things; so long as they're done in an actually safe manner by professionals.

But, as I said before, if the DEA believes it has the power to stop that none-the-less; that's what they will do, without respect to if the law is actually legally unclear or borderline. Unfortunately many pharmaceutical places don't care to invite the wrath of the DEA; even if what they're doing could be considered permissible; so long as they do not synthesize an exact drug that the Feds specifically name as a controlled substance.

Again; IANAL either. But I do think there's a lot of room for small compounding pharmacies to synthesize various drugs to meet a patient's needs quickly while waiting for proper shipments to arrive. There's lots of compounds that are life-sustaining that do not fall under the DEA banner of authority.