Nine states have legalized the medical use of marijuana. (ABCNEWS.com)

A Federal Offense Supreme Court Keeps Medical Marijuana Illegal By Jackie Judd W A S H I N G T O N, May 14 — The Supreme Court declined today to make an exception that would legalize the medical use of marijuana under federal law.

Federal law labels marijuana an illegal "controlled substance." And in a unanimous 8-0 ruling, the high court ruled that patients with debilitating diseases who take the drug to relieve their pain would be doing so illegally.

"Congress has made a determination that marijuana has no medical benefits worthy of an exception," Justice Clarence Thomas wrote in the opinion.

The decision infuriated medical marijuana advocate Angel McClary, "The Supreme Court has American human blood on their hands. I can tell you I am not willing to die. I am not willing to be a martyr."

Nine states have legalized the medical use of marijuana. Tens of thousands of people in advanced stages of cancer, AIDS and other diseases smoke legally obtained marijuana, saying that it relieves their suffering.

The Supreme Court's ruling does not overturn those state laws, but it leaves medical marijuana users open to prosecution by the federal government.

Advocates of medical marijuana were disappointed by the court's ruling, saying it would have a chilling effect on the medical use of the drug.

"Our hope is the federal government is not going to go and reach down and pull people who get caught with very small amounts of marijuana, using it for medical purposes, and elevate them to a federal case," said Allen St. Pierre, executive director of the NORML Foundation (NORML stands for the National Organization for the Reform of Marijuana Laws).

The medical community is divided over the issue. A government study concluded the drug does ease pain and nausea but it also delivers "harmful substances." The study recommended further examination of the issue.

"When you look at marijuana today, there's no reason to assume it's a good medicine or bad medicine. But it may well be a quack medicine that provides no help to people," said Joseph Califano, director of the National Center on Addiction and Substance Abuse at Columbia University.

Justice Stephen Breyer did not vote on the ruling because his brother, U.S. District Judge Charles Breyer, presided over the original 1998 case, in which federal prosecutors sought an injunction against six distributors of medical marijuana in California.

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