That familiar odor wafting from San Francisco street corners, storefronts, and the neighborhood growhouse? It's the smell of legality. Medical cannabis is the law of the land in California, 14 other states, and the District of Columbia. Yet, as many marijuana users will tell you, protection under state law hasn't guaranteed protection under federal law at all.

It was more obvious under the George W. Bush administration, which pledged to "ignore" state medical marijuana laws and go after marijuana users. For eight years, the federal government "subverted" the will of the states, according to the ACLU, and in the process ignored the Constitution's guarantees of state sovereignty, as many a pot user has tried to argue in court.

So when Barack Obama's new administration delivered a message on medical marijuana in February 2009, it was heard loud and clear: The federal government was getting out of the business of busting pot in California and other states where voters had approved medicinal application of the plant. Obama the candidate promised as much during the campaign, and now the new attorney general, Eric Holder, had made it so by issuing guidelines protecting those following state law. Federal policy on medical marijuana had changed.

For that campaign promise — and for pledges to end the Iraq war and reform health care — Obama won many votes from San Franciscans, including people like the 30 medical cannabis users gathered at a former brothel on Mission Street on a recent evening. The low- and no-income folk who constitute the patient advocacy and activist network Axis of Love cannot use their Medicare and Medi-Cal benefits to buy their preferred tonic — federal law makes it thus — and so they must rely on the charity of a few San Francisco cannabis dispensaries for their medicine. Pot and meals are dispensed daily, free of charge, under the supervision of activist Shona Gochenaur. "Obama got a ton of votes from our community," she says, "for the many campaign promises he made that things would change."

That the man in the White House was even willing to put "medical" and "marijuana" together in the same sentence was a step forward for California's cannabis advocates. They had endured such spectacles as the sentencing to five years in federal prison of a pair of El Dorado County providers — Mollie Fry, a breast cancer survivor, and Dale Schafer, a hemophiliac — and the DEA seizing six plants belonging to Angel Raich, who had an inoperable brain tumor. Legal outdoor growers were living in fear after an unprecedented string of DEA raids in the state's pot-producing counties in 2007. In the Bay Area, the U.S. Attorney's Office, headed in the last years of Bush's presidency by Reagan appointee Joseph Russoniello, sought stiff sentences against two brothers for running a dispensary in Hayward.

To hear Obama say change had come to California's pot users was welcome balm indeed. That Obama's DEA had raided dispensaries in Los Angeles, Lake Tahoe, and San Francisco was an aberration, the White House said: Our guys aren't in yet.

Enforcement is still needed. There are plenty of straight-up pot dealers out there, including some unscrupulous types posing as "medical" marijuana enterprises, not to mention Mexican cartels growing thousands of plants in national forests. Exactly how many of these outlaws are getting busted, and how many legitimate, state-law-abiding operations get swept up with them, the government can't say. "We don't keep track of cases that way," says Jack Gillund, spokesman for the local U.S. attorney.

One man sitting at Axis in what was once the brothel's waiting room, declining pulls from the bags full of marijuana vapor the Axis members pass around, could tell you all about federal enforcement. If Scott Feil had the time, he'd explain how he was the first California medical cannabis dispensary owner to beat an alleged drug asset forfeiture in court, which found no wrongdoing at the dispensaries in Los Angeles and Ukiah he'd run in the infancy of the medical marijuana movement.

But he can't stay. "I've got this thing strapped to my ankle," he says by way of apology, lifting one trouser leg to reveal the homing device attached there. He is one of the Californians the Justice Department wants to put away for committing crimes for which the state of California provides business licenses.

Feil can tell you that much of what is going on at Axis is a violation of the federal Controlled Substances Act, which neither Obama nor Holder have changed one bit. He is one of at least 74 state-licensed medical marijuana providers raided nationwide under the Obama administration. "Everybody assumes that the president and Holder were saying, 'It's okay, it's okay,'" he says. "But that's absolutely not what they're saying. Yet that's the way the public heard it. Thousands of people think that."

Put another way, "the United States government said it was okay for me to grow weed," says Tom Carter, a Lake County contractor who faces 10 years for allegedly selling 500 marijuana clones — tiny seedlings that are not counted as marijuana under state possession laws — to an undercover federal agent posing as the owner of a legal dispensary. "And now they're coming back and saying that I can't? That's bullshit."

"Know what I think?" he adds. "Barack Obama and Eric Holder are lying sacks of shit."

Most Democratic politicians swing to the center when taking their games national. One of Obama's sharpest shifts may have been on marijuana. There was a time when he thought pot should be decriminalized — sort of. "The war on drugs has been an utter failure," the newly elected senator told a Chicago audience in 2004. "We need to rethink and decriminalize our marijuana laws." That remark drew a smattering of applause before he amended it with, "but I'm not someone who believes in legalization."

On the presidential campaign trail in 2008, Obama displayed a "practical view, more than anything else," he said, when asked about medical pot when he and Hillary Clinton were jockeying for liberal votes. If his position had shifted, he said, it was still one from which he could still dispense his favorite tonic — hope — to medical marijuana users. "If it's an issue of a doctor prescribing medical marijuana to a glaucoma or a cancer patient... really, there's no difference between that, and the doctor prescribing morphine or anything else," he said. Spending "political capital" on marijuana reform was "not likely ... but what I'm not going to be doing is using Justice Department resources to circumvent state law on this issue."