SAN FRANCISCO -- Hundreds of medical marijuana activists gathered on the steps of City Hall Tuesday to support California's multi-million dollar cannabis industry, under siege since the federal government launched an aggressive crackdown last fall.

A handful of local legislators and cannabis patients addressed the heated crowd before marching down the street to the federal courthouse to address U.S. Attorney Melinda Haag, who has championed anti-marijuana actions in the Bay Area.

"We're patients, not criminals!" the protesters chanted, along with cries of "DEA, go away!" and "Fire Haag!"

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"Today, we are all green," said San Francisco Board of Supervisors President David Chiu in a fiery speech. Chiu and fellow city supervisors who attended the event pledged to expedite the permitting process for local pot shops that have been forced to close and wish to reopen elsewhere.

California's medical marijuana industry has been struggling since federal prosecutors began targeting dispensaries in October. More than 100 California busineses have been forced to shut down, and hundreds more have received threatening letters claiming their landlords could be jailed if they continue to operate.

Five cannabis clubs in San Francisco have shuttered, leaving employees without work and patients without access to their medicine. Haag sent the same threatening letters to roughly a dozen more (some dispensaries won't go on the record as to whether they had received a warning). On Monday, federal authorities raided Oakland's world-famous Oaksterdam University and the home of its founder, Richard Lee, one of the state's most outspoken medical marijuana activists.

The U.S. attorneys' actions mark a sharp departure from the Obama administration's 2009 Ogden Memo, which declared that prosecutions in states that have legalized the plant for medicinal purposes would not be a priority. Advocates argue the federal government should direct its energy elsewhere.

"It's a total waste of federal resources," Stephanie Tucker, spokesperson for the San Francisco Medical Cannabis Task Force, told The Huffington Post. "They're attacking a peaceful, regulated community and it's wasting money. Shame on them."

Though the drug remains illegal under federal law, California became the first state to legalize cannabis for medicinal purposes when voters passed Proposition 215 in 1996. Studies have shown that California's medical marijuana industry generates upwards of $100 million in annual tax revenue.

Haag has remained relatively mum on the issue, repeatedly citing dispensaries' proximities to schools and parks as justification for the crackdown. "I hope that those who believe marijuana stores should be left to operate without restriction can step back for a moment and understand that not everyone shares their point of view," she told HuffPost in a statement. "People are deeply troubled by the tremendous growth of the marijuana industry and its influence on their communities."

But advocates said they believe Haag's argument thin. Cathy Smith, co-founder and manager of HopeNet, a dispensary in San Francisco's SoMa neighborhood, told HuffPost that the neighborhood has become dramatically safer in the nine years since her business opened its doors. Crime has dropped significantly, largely due to the increased presence of lighting and surveillance cameras her store installed in order to adhere to the city's strict regulations surrounding cannabis clubs.

"Nine years ago I wouldn't be open past 5 p.m. because I was worried about our female customers," Smith said. "Now we're open until 9. The neighborhood has improved that much."

So much, in fact, that a few years ago, a private school opened around the corner. And now HopeNet's landlords have received their own threatening letter from Haag because of the shop's proximity to that school.

"Haag says she can't tell the difference between a good club and a bad club," Smith said. "I'm here to show her the difference. We are the club that is different; there's no question about it."

In addition to selling medical marijuana and related supplies, HopeNet offers a series of weekly community events, including a veterans' support group, a ladies' afternoon tea and various life skills workshops. "We like to think of ourselves as a family," Smith said. "We don't just sell pot here -- we help people."

And the family is willing to fight. Supporters of Smith's business have sent hundreds of handwritten letters to Haag's office demanding she back off, and others have tried (unsuccessfully) to schedule in-person meetings.

Similar to the HopeNet's community's outpouring of support, he actions of Haag and her counterparts have served to strengthen the ties of pot proponents across the Bay Area. "It's only emboldening us and bringing us together," said Tom Angell, spokesman for Law Enforcement Against Prohibition, a coalition of active and retired police officers, prosecutors and judges who actively speak out against the drug war. "People who used to compete in the marketplace are now standing shoulder to shoulder."

Advocates have drawn the endorsements of a fair share of legislators, as well. California Assemblyman Tom Ammiano (D-S.F.) recently introduced a measure that would establish uniform regulations for pot shops throughout the state based on San Francisco's strict and successful standards for operating dispensaries. On Monday, a coalition of lawmakers from five states penned an open letter to the Obama administration demanding an end to the crackdown.

Meanwhile, as some San Francisco cannabis clubs close down, others plan to open. Last month, the planning commission approved three new dispensaries for the city's Excelsior district, and another opened in the Mission last week.

Those targeted by federal authorities vow to defend their businesses and the industry until the end. "They can indict me any day. They can arrest me at any time," Lee said during Tuesday's rally. "One way or another, Oaksterdam will fight on."

So will San Francisco.

Take a look at images from Tuesday's demonstration below:

PHOTO GALLERY