The question will probably rest on whether the religion predates the regulation. This could be a precedent regarding multiple wives and Mormonism, etc. But if we moved back to the original understanding, a state legislature could ban the practice, if necessary.
Another question, could a person be denied employement for failing a drug test because of "religious drug use"?
For the record, polygamy is banned by the Utah Constitution, not by the Federal government. Way back in the day when people still understood what enumerated powers meant (when incidentally Federal prohibition laws didn't exist) it was acknowledged that the Federal government did not have the power to prohibit polygamy in a State. So, in order for Utah to become a State, they were required to enshrine polygamy bans in their Constitution, since the Federal territorial ban would be invalid upon Statehood.
Don't think so.
Not unless the People gave the legislature the authority to tell them what they could possess or ingest.
Oh, that's right. The People, not possessing that restrictive power ourselves, are incapable of giving something we don't possess to anyone.
Darn! It's that pesky Freedom thing again. :-)