"I'm going to have to be prepared to be arrested," said Diane Monson, who smokes marijuana several times a day to relieve back pain.

Monson, 48, of Oroville, was prescribed marijuana by her doctor in 1997 after standard prescription drugs didn't work or made her sleepy. She is battling degenerative spine disease.

"I'm way disappointed. There are so many people that need cannabis," Monson said.

The Bush administration had argued that states, even the 10 states with medical marijuana laws, could not defy the federal Controlled Substances Act, which declares marijuana to be not only illegal, but of no medical value. Justice John Paul Stevens, writing the 6-3 decision, said that Congress could change the law to allow medical use of marijuana.