A man attempted to argue this yesterday in Colorado and was subsequently jailed for his choice of religion. The supreme court has already ruled on this issue; American's don't have the right to religious freedom unless that religion is approved for use by the United States Government.

From the Denver Post (yesterday): http://www.denverpost.com/headlines/ci_14643334 (pasted below)

GEORGETOWN — In what is likely a first-of-its-kind case in Colorado, a judge here convicted an Avon man of marijuana possession Tuesday, despite his claim that the charges violated his First Amendment rights because he needs cannabis for religious purposes.
Trevor Douglas, 25, told the court he uses cannabis as a religious sacrament, similar to the use of bread and wine in Catholic Holy Communion. He holds membership in two churches that espouse such beliefs and said he was trained by his parents to use marijuana in holy ceremonies.
"I believe that, as mentioned in the Bible, cannabis is the tree of life," Douglas, acting as his own witness, said at his two-hour trial. "I hold the plant very sacred to myself. Obviously it is very sacred to my church. I couldn't envision my life or my church without it."
Throughout his testimony, Douglas thumbed through pre-marked passages in a Bible — defense exhibit No. 3 — that he believes reference cannabis.
"It is a way of communicating with God," Douglas said. "I truly believe that it is the botanical messiah."
Douglas sparred with prosecutor Michael Angel over whether the Bible truly substantiates his beliefs.
"They actually never say 'cannabis,' " Angel said, referring to the Bible passages. "They say a different word that your religion has interpreted to mean cannabis."
A Colorado State Patrol trooper stopped Douglas in August for having an expired vehicle registration. During the stop, the trooper smelled marijuana, which Douglas willingly handed over while explaining it is part of his religion.
Douglas pleaded guilty to the expired registration charge Tuesday but went to trial over marijuana and drug paraphernalia charges, both petty offenses.
Douglas' attorney, Rob Corry, said cannabis is integral to Douglas' religion, making his possession of it protected under the First Amendment.
But Clear Creek County Judge Rachel Olguin-Fresquez took a narrower approach.
It wasn't that Douglas was faking his beliefs, Olguin-Fresquez said. Instead, the issue was whether his personal spiritual practices — and those of his fellow adherents — amount to a religion as defined in case law.
"It does not appear to this court that the defendant is practicing a religion so much as his own beliefs," she said.
Olguin-Fresquez sentenced Douglas to perform 30 hours of community service and pay several hundred dollars in fines. Douglas said he plans to appeal.
John Ingold: 303-954-1068 or jingold@denverpost.com

Read more: http://www.denverpost.com/headlines/ci_14643334#ixzz0huHhqKhH

I had read somewhere that some one had been to the S. Court and won defending their So. American religious practice of using an intoxicating plant for ceremonial purposes. Maybe able to site the ruling as defense. Sorry that I can't be any more specific, see so much stuff, hard to remember where it came from.

You can claim it now, and if it works, could legally buy weed from the cops.