Medical cannabis advocates and patients met in San Francisco Tuesday to hold a rally condemning the federal government’s crackdown on medical cannabis dispensaries in California.

Several hundred people gathered on the steps of City Hall at 11:30 a.m. for the rally, which was sponsored by Americans for Safe Access and San Francisco United, a campaign aimed at encouraging city officials to protect access to medical cannabis. Many of the attendants were patients or business owners affected by the crackdown that began last fall.

Although medical marijuana was legalized in the state in 1996, the federal government has said that marijuana is still a federally controlled substance and therefore falls under federal regulation.

Several members of the San Francisco Board of Supervisors voiced their support for medical cannabis access in California to the crowd at Tuesday’s rally, while the San Francisco District Attorney George Gascon and state Assemblymember Tom Ammiano (D-San Francisco) sent along statements supporting safe access for patients.

“We’re here to send a clear message to the federal government that San Francisco marijuana programs are fully supported by the city government,” said Stephanie Tucker, one of the organizers for the event and a member of the Medical Cannabis Task Force that advises the board on medical cannabis issues.

Supervisor David Chiu told the crowd that he hopes growing support from the public and continued efforts within the medical marijuana community will eventually sway federal opinion.

“There are some confused attorneys in Washington who need to understand that we are standing on the right side of history on this issue,” Chiu said at the rally.

Protesters marched down the street to the federal building on Golden Gate Avenue where U.S. Attorney Melinda Haag’s office is located. Haag’s involvement with the federal crackdown has resulted in several San Francisco dispensaries closing their doors under threat of legal action.

Charles Pappas — a member of Berkeley’s Medical Cannabis Commission and the owner of a San Francisco dispensary which was forced to close last fall — spoke about his frustration with the Department of Justice’s actions against medical cannabis businesses.

“I’ve written five letters to Obama, three or four to (U.S. Attorney General) Eric Holder and five to the governor,” said Pappas, who added that he also sent Haag 50 testimonials in support of medical cannabis when she met with Ammiano in December.

The U.S. Drug Enforcement Administration raided Oaksterdam University in Oakland Monday afternoon, reportedly as part of a criminal investigation. While Oaksterdam has been allowed to remain open, marijuana advocates say this is just the latest in a series of intimidation efforts by the federal authorities.