The federal government has the power to prevent sick patients from smoking home-grown marijuana that a doctor recommends to relieve chronic pain, a divided U.S. Supreme Court ruled on Monday in a setback for the medical marijuana movement.

The 6-3 ruling means the federal government can enforce a federal law prohibiting the cultivation, possession and use of medical marijuana even in the 10 states where it is legal under state law.

Justice John Paul Stevens wrote for the court majority that the federal law, the Controlled Substances Act of 1970, was a valid exercise of federal power by the U.S. Congress "even as applied to the troubling facts of this case" involving two seriously ill California women.

Angel Raich has an inoperable brain tumor and other medical problems while Diane Monson suffers from severe back pain. Their doctors recommended marijuana for their pain.

"Just because we did not win this battle does not mean that we will not still have the opportunity to win this war," Raich said in Oakland, Calif. She urges Congress to change the law to allow medical use of marijuana.

"If I were to stop using cannabis unfortunately I would die," the 39-year-old Raich told reporters. "This is the only way I have to combat my suffering."

Stevens wrote that the question before the court was not whether it was wise to enforce the federal law in these circumstances, but only whether Congress has the power to adopt such a law.

He wrote that the democratic process might be more important than the legal challenges and added that supporters of medical marijuana "may one day be heard in the halls of Congress."

The ruling was a victory for the Bush administration. It estimated as many as 100,000 Californians would use marijuana for medical purposes if the Supreme Court ruled for the two women.

John Walters, the White House drug czar, said in a statement, "Today's decision marks the end of medical marijuana as a political issue." Supporters of medical marijuana disagreed.

"The power of state governments to enact and enforce state medical marijuana laws is not affected by the Supreme Court's ruling," says Allen Hopper of the American Civil Liberties Union's Drug Law Reform Project.

Dan Abrahamson of the Drug Policy Alliance says, "The federal government still has a choice--it can waste taxpayer dollars by going after sick and dying patients or go after individuals who pose a real danger to society."

Barbara Bergman, president-elect of the National Association of Criminal Defense Lawyers, says, "If our Constitution means anything, it should mean that the 'war on drugs' cannot be made to be a war on the quality of life of chronically or terminally ill Americans."

But Stevens wrote that the court agrees with the government's argument that an exception for medical marijuana would leave a "gaping hole" in the federal drug law.

He wrote that federal law prevails over the California law, which voters approved in 1996. Alaska, Colorado, Hawaii, Maine, Montana, Nevada, Oregon, Vermont, and Washington have similar laws.

Chief justice William Rehnquist and justices Sandra Day O'Connor and Clarence Thomas dissented. They wrote that states should be free to set their own laws. (Reuters)