Medical marijuana advocates were ecstatic Monday at word that the Obama administration is backing off prosecution efforts in California and 13 other states that allow use of the drug in treating pain and other ailments.

But they remained concerned that the new policy announced Monday is still vague and that oversight of marijuana dispensaries remains a hodgepodge of local regulations.

"It's going to mean a sigh of relief for those that are doing the right thing, an acknowledgment that you don't have to worry about being prosecuted," said Lanette Davies, who operates Canna Care, a medical marijuana dispensary in North Sacramento.

"Even though you know you're doing the right thing, you're paying taxes, you have a business license, still it was always there in the back of my mind," Davies said. "I've never even had a speeding ticket, and yet I could have done 10 years in prison for providing for patients, so knowing now that the federal government won't come in is a big relief."

California voters approved the use of marijuana for medical reasons in 1996, and since then marijuana dispensaries have opened the length of the state to provide the drug to patients with physician referrals.

But for years, the federal government refused to recognize the law, and the Clinton and Bush administrations pursued prosecutions against medical marijuana providers.

The Obama administration had indicated it did not intend to continue that policy, and on Monday the Justice Department issued a series of guidelines to U.S. attorneys in the states with medical marijuana laws, telling them, in essence, that they have more important cases to pursue.

"It will not be a priority to use federal resources to prosecute patients with serious illnesses or their caregivers who are complying with state laws on medical marijuana," U.S. Attorney General Eric Holder said in a statement, "but we will not tolerate drug traffickers who hide behind claims of compliance with state law to mask activities that are clearly illegal."

Some advocates say the upshot is that the federal government is going to leave the policing of medical marijuana in the hands of the states.

"It is a significant step," said Bruce Mirken, spokesman for the Marijuana Policy Project in San Francisco. "It is overall the biggest and most positive change in federal policy in medical marijuana in at least 30 years."

But many questions remain about how marijuana dispensaries will be dealt with statewide. Currently, there is no agency regulating dispensaries – tracking how many have opened, how and where they operate, and whether, as required under state law, they do not make a profit.

California Attorney General Jerry Brown issued his own set of guidelines in August 2008 for how dispensaries should operate. But local governments, police agencies and prosecutors have great leeway in how they address the issue.

In San Francisco and Oakland, for instance, medical marijuana advocates say the dispensaries are accepted with little controversy.

In Sacramento, a task force is preparing a draft set of city guidelines that may be unveiled next month.

In Los Angeles, the City Council passed an ordinance in 2007 banning new dispensaries and tightened it last July. But a judge on Monday issued an injunction against enforcing the ordinance.

And in September, local and federal officials raided 14 dispensaries in San Diego County and shut them down. San Diego County District Attorney Bonnie Dumanis said the action was aimed at "drug dealers hiding behind the state's medical marijuana law."

Some marijuana advocates said Monday's Justice Department announcement does not guarantee that individual U.S. attorneys cannot decide on their own to pursue cases against lawful dispensaries.

"It's a nice statement, but it has a lot of big loopholes in it," said Dale Gieringer of the California office of the National Organization for the Reform of Marijuana Laws.

Lawrence Brown, the U.S. attorney in Sacramento, referred questions about the policy to the Justice Department in Washington.

But he said his office recently changed its policy to excuse from prosecution people found to possess small amounts of marijuana on federal lands if they have a valid recommendation under the state's medical marijuana law.

This came after defense attorneys pointed out that a series of such cases were set for trial and asked for review in light of statements Holder had made in recent months regarding medical marijuana.

After the review, Brown's office dismissed those cases, but the U.S. attorney said the new policy is not a blanket authorization for people to have marijuana on federal lands.

For instance, someone who is smoking marijuana and creating a disturbance could be prosecuted, as could someone smoking in front of children or driving under the influence of the drug.

There are no circumstances under which medical marijuana would be allowed on military bases, he said.

While the new guidelines issued by the Justice Department were seen by many as a step forward for use of medical marijuana, people who were prosecuted under the old policies will see no benefit.

Bryan Epis, who in 1997 became the first person to be arrested in a federal prosecution of medical marijuana in California, has served more than two years of a 10-year prison sentence. He is out pending an appeal.

"I was totally following state law," Epis said Monday from Chico, "and I should totally be covered by this (new policy)."

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