OAKLAND, Calif., Jan. 20 — As a marijuana celebrity, Ed Rosenthal has been on a career roll. The author of a dozen cannabis self-help books and a magazine advice column, "Ask Ed," Mr. Rosenthal is the pothead's answer to Ann Landers, Judge Judy, Martha Stewart and the Burpee Garden Wizard all in one.

Can't get rid of the powdery mildew on your cannabis seedling? Try a 20 percent skim-milk solution. The feds got you in court on charges of cultivation? Challenge their crop yield estimates. Want a high without the harmful tar? Use a pipe that vaporizes it.

Mr. Rosenthal's renown has taken him to the Senate, where he testified about marijuana sentencing laws, and to a dozen foreign countries, where he worked as a consultant to hemp and marijuana growers. Throughout it all, he has carried on with impunity.

Until now.

On Tuesday, Mr. Rosenthal goes on trial in federal court in San Francisco on charges of marijuana cultivation and conspiracy. The charges stem from a business he ran growing marijuana to be sold for medicinal uses under the auspices of the City of Oakland's medical marijuana ordinance, one of many such municipal statutes in California.

If convicted on all counts, Mr. Rosenthal, who is 58, faces a minimum sentence of 10 years in prison; the conspiracy charge carries a possible life sentence.

The trial has riled his many fans in the marijuana community, but its implications are far broader. At its core, Mr. Rosenthal's prosecution exposes a deepening rift between the State of California and the Bush administration over the use of marijuana for medicinal purposes, with no middle ground for compromise in sight.

On one side, federal law enforcement officials view Mr. Rosenthal's arrest and possible conviction as a trophy in the stepped-up war on drugs.

"There shouldn't be any doubt about our determination to enforce the laws of the United States," said Special Agent Richard Meyer, a spokesman for the federal Drug Enforcement Administration in San Francisco. "Marijuana is illegal regardless of the intended use, regardless of the person cultivating it and regardless of where it originated."

On the other side, some state and local officials regard Mr. Rosenthal's prosecution as an effort by the federal government to subvert the 1996 statewide voters' initiative, known as Proposition 215, that made marijuana legal for medicinal purposes. Since that initiative passed in California, eight other states have approved similar laws.

"I am just speechless," said Nathan A. Miley, an Alameda County supervisor who helped write the ordinance in Oakland when he was a councilman. "What we were attempting to do through the city was put together as tight a medical practice as possible. Ed was just part of that whole effort."

A handful of court cases have failed to defuse the federal-state tensions. In the most significant ruling, the United States Supreme Court decided in 2001 that under federal law "medical necessity is not a defense to manufacturing and distributing marijuana."

But the ruling did not address Proposition 215 and whether it violated federal law. Moreover, it involved an organization, not an individual, and it arose from civil litigation, not a criminal case. And rulings by other courts since then have offered some protections.

Last July, the California Supreme Court ruled that Proposition 215 granted medical users of marijuana "limited immunity from prosecution" under state law. In October, a federal appeals court in San Francisco decided that the federal government may not revoke the licenses of doctors who recommend marijuana to their patients.

"This is a huge conflict," said Hallye Jordan, a spokeswoman for Attorney General Bill Lockyer, California's top prosecutor and a supporter of the state statute. "State law legalizes medical marijuana and federal law makes marijuana illegal. Period."

In a letter to Asa Hutchinson, the administrator of the federal drug agency, Mr. Lockyer characterized a flurry of federal raids on medicinal marijuana providers last fall as "wasteful, unwise and surprisingly insensitive." In pointing a finger directly at the Bush administration, Mr. Lockyer's office reported that federal efforts against "authorized California cooperatives" began only in 2001.

"While I am acutely aware that federal law conflicts with California's on this subject and needs to be reconciled, surely an administration with a proper sense of balance, proportion and respect for states' rights could and should reconsider the D.E.A.'s policy and redirect its resources," Mr. Lockyer wrote.

In a reply, Mr. Hutchinson rejected the notion of medicinal marijuana as unsound, legally and scientifically. He also mocked the suggestion that a voters' initiative might change that. The Food and Drug Administration, he wrote, "has never in the past approved medicine by popular referendum, and I believe it would be ill advised to set the precedent now."

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Robert V. Eye, a criminal lawyer from Topeka, Kan., who is representing Mr. Rosenthal, said his client was caught in the legal crosswinds of difficult social change.

"Ed is a friction point between these competing interests," Mr. Eye said. "It is remarkable to see this social change on the ground."

Mr. Rosenthal says it was never his intention to be drawn into the legal tug of war. He and his wife, Jane Klein, run a publishing business out of their hillside home here, a picture-book Victorian with a lush garden and terraced backyard. When Mr. Rosenthal was arrested last February for growing marijuana plants in a warehouse in an industrial area near the Port of Oakland, he was engaged in what was more of a hobby than a business, he said.

"I already have my business," he said. "To me, this was a chance to do work in the field. My profit out of it is the books. I could write about what I learned."

Oakland is among the cities and counties in California that have enacted ordinances to permit marijuana for medicinal purposes under Proposition 215. The law allows seriously ill people, who have a doctor's recommendation, to cultivate and use marijuana as a form of treatment.

Officials in Oakland, where drug abuse and streets sales of narcotics are a serious problem, concluded that it would be better to offer marijuana to sick people in a regulated environment than to have them purchase it on the street. Even before the state initiative, the City Council instructed the police not to pursue crimes "regarding the distribution of marijuana for compassionate medical use."

Beginning in the early 1990's, Mr. Rosenthal devoted much of his research and writing to exploring the medicinal benefits of marijuana. His most recent book looks at the multiple varieties of marijuana, with the long-term objective, he said, of better determining which ones might be most effective in alleviating the symptoms of diseases like cancer, AIDS, multiple sclerosis and depression.

"I started experimenting with marijuana in the 1960's," Mr. Rosenthal said. "When the 60's ended, I continued into the 70's. Now it is sort of like a Framingham study: I am working on a life study."

Mr. Rosenthal's interests and Oakland's needs matched. By 1998, he was deemed "an officer of the city" under the city's ordinance and was growing thousands of marijuana starter plants at the West Oakland growing facility. At the time of his arrest, federal agents seized 3,163 plants.

Mr. Rosenthal had sold starter plants to a variety of cooperatives and medical marijuana clubs in Oakland and the Bay Area that dispense marijuana as medicine. Among his customers was the Harm Reduction Center in San Francisco, where federal agents seized 714 marijuana plants the same day Mr. Rosenthal was arrested. According to the indictment against Mr. Rosenthal, an undercover federal agent and a "confidential source" bought 405 marijuana plants at the Harm Center in January 2002 for $3,600.

Barbara J. Parker, Oakland's chief assistant city attorney, said the city ordinance was written expressly to give immunity under the federal Controlled Substance Act to people carrying out the ordinance's provisions. Ms. Parker said the immunity was the same kind afforded to police officers and other public officials who enforce laws related to controlled substances.

"The federal government didn't come after the city and say this ordinance can't stand," Ms. Parker said. "They didn't come after the state and say this proposition can't stand. Instead, they are going after individuals. That makes this very difficult."

Mr. Rosenthal said he had never been told that he was doing anything wrong or even given a hint that the city's ordinance might be "pushing the limits of the law." By prosecuting him, Mr. Rosenthal said, the Justice Department had put the judge, Charles R. Breyer of United States District Court, in the untenable situation of the commander of the ship in Melville's "Billy Budd."

"He knows Billy Budd shouldn't be punished, but he is just following the law," Mr. Rosenthal said. "Ultimately, because of the law, Billy Budd winds up hanged."

It seems George L. Bevan Jr., the assistant United States attorney prosecuting the case, anticipated such an argument. In a recent motion to exclude medicinal marijuana as a possible defense for Mr. Rosenthal, Mr. Bevan declared: "Ignorance of the law or a mistake of law is generally no defense to a criminal prosecution."

Judge Breyer granted the motion.