Yeah, the reason they make exceptions for spiritual use of drugs, if I remember correctly, was because some Native American tribes fought for their right to use peyote spiritually like their ancestors had for thousands of years. The government then decided that the Native Americans could have their peyote because of freedom of religion, but they also knew that just letting anybody use any drug for religious purposes is essentially the same thing as legalizing all drugs. They're not stupid. Well, not that kind of stupid.

So yes, you will be arrested even if you claim it's religious. Just ask the Rastafarians (who for some reason aren't allowed to take advantage of the same freedom of religion clause as the peyote-eating Native Americans).