San Francisco ? Ed Rosenthal, the self-proclaimed “Guru of Ganja,” walked free Wednesday after a federal judge sentenced him to just one day in prison for growing marijuana Rosenthal said was for medical purposes. He could have gotten 60 years behind bars.

U.S. District Judge Charles Breyer said Rosenthal genuinely believed that what he was doing was not against the law.

Rosenthal’s case represented the latest clash between state and federal authorities over the medical use of marijuana. The federal government does not recognize medical marijuana laws in California and the eight other states that have them.

Wednesday’s decision was met by cheers and applause in the courtroom. Federal prosecutors had asked for a 6 1/2-year prison term.

“I think it’s a marvelous victory for states’ rights and the medical use of marijuana,” said Keith Stroup, executive director of the National Organization for the Reform of Marijuana Laws. “It sends a strong signal to the federal government that they should reconsider their current program of arresting patients and caregivers in California.”

In January, a jury concluded Rosenthal was growing more than 100 plants, conspired to cultivate marijuana, and maintained an Oakland warehouse for a growing operation.

Rosenthal, 58, had said he was acting as an agent for Oakland’s medical marijuana program, an outgrowth of a 1996 measure approved by California’s voters that allows sick people to obtain marijuana with a letter from a doctor.

The judge sentenced Rosenthal to one day in prison, then set him free after crediting him with time already served, saying the defendant “had a reasonable belief that what he did was not contrary to law.”

Rosenthal also was fined $1,300 and will be on supervised release.

Federal law does not permit legalization of marijuana for medical use, although Alaska, Arizona, California, Colorado, Hawaii, Maine, Nevada, Oregon and Washington allow it.