The high court ruled that a federal law outlawing marijuana applied to two seriously ill California women, even though California is one of at least nine states that allow medical use of marijuana.

Justice John Paul Stevens said for the court majority that the federal law, the Controlled Substances Act of 1970, was a valid exercise of federal power by the Congress "even as applied to the troubling facts of this case."

By a 6-3 vote, the justices set aside a lower-court decision in favor of the two women.

It represented another setback for the medical marijuana movement. The high court ruled in 2001 that California cannabis clubs may not distribute marijuana as a "medical necessity" for seriously ill patients.

The latest ruling stemmed from a lawsuit brought in 2002 by Angel Raich, who has an inoperable brain tumor and other medical problems, and Diane Monson, who suffers from severe back pain. Their doctors recommended marijuana for their pain.

Monson cultivates her own marijuana while two of Raich's caregivers grow the marijuana and provide it to her free of charge. In 2002, Drug Enforcement Administration agents destroyed six cannabis plants seized from Monson's home.

Their attorney, Randy Barnett of Boston, argued that medical use of home-grown marijuana falls outside the power of Congress to regulate trade among the states and that only marijuana provided relief from the pain the two women suffer.

The ruling was a victory for the Bush administration, which appealed to the Supreme Court after a federal appeals court in California said that marijuana used for medical purposes was different from drug trafficking.

The administration estimated that as many as 100,000 Californians would use marijuana for medical purposes if the Supreme Court ruled for the two women.

Government lawyers said it would be difficult to enforce the nation's drug laws if there was an exception for medical marijuana. They said the federal ban trumped the California law, which the voters adopted in 1996 to allow "compassionate use" of medical marijuana.

The appeals court said states could adopt medical marijuana laws as long as the marijuana was not sold, transported across state lines or used for nonmedicinal purposes.

The Supreme Court set aside that ruling.

Stevens said the power of Congress to regulate commerce among the states includes the authority to prohibit the local cultivation and use of marijuana in compliance with California law.

Chief Justice William Rehnquist and Justices Sandra Day O'Connor and Clarence Thomas dissented.

"This case exemplifies the role of states as laboratories," O'Connor wrote.

"Relying on Congress' abstract assertions, the court has endorsed making it a federal crime to grow small amounts of marijuana in one's own home for one's own medicinal use," she said. "This overreaching stifles an express choice by some states ... to regulate medical marijuana differently."