California Attorney General Bill Lockyer said he was disappointed with the ruling, but not surprised, and that 'people shouldn't panic ... there aren't going to be many changes.' Local and state officers handle nearly all marijuana prosecutions and must still follow any state laws that protect patients.

"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.

The Supreme Court ruled that federal authorities may arrest and prosecute people whose doctors recommend marijuana to ease pain, concluding that state laws do not protect users from a federal ban on the drug.

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.

Backyard Crop Seized

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.

Fifty-six percent of California voters approved the nation's first so-called medical marijuana law in 1996, allowing patients to smoke and grow marijuana with a doctor's recommendation.

Even though the state law was on the books, Monson's backyard crop of six marijuana plants was seized by federal agents in 2002. She and Angel Raich, the other plaintiff, sued then-Attorney General John Ashcroft.

"If I stop using cannabis, unfortunately, I would die," said Raich, who estimates her marijuana intake to be about nine pounds a year.

Raich, 39, suffers from scoliosis, a brain tumor, chronic nausea and other problems. She said she uses marijuana every few waking hours, on the advice of her doctor, who said dozens of other medications were of little help.

Federal Law 'Illogical'

Many other cannabis clubs still operate openly in California and other states, but have taken measures -- such as not keeping client lists -- to protect their customers from arrest.

California Attorney General Bill Lockyer said he was disappointed with the ruling, but not surprised, and that "people shouldn't panic ... there aren't going to be many changes."

Local and state officers handle nearly all marijuana prosecutions and must still follow any state laws that protect patients.

"Nothing is different today than it was two days ago, in terms of real world impact," Lockyer said. "There's a California law which conflicts with the federal law. Federal law treats heroin and marijuana the same, which is illogical."