"The city of Oakland believes in compassionate care," said Paul Rose, spokesperson for Oakland's mayor Ron Dellums.

"The people of California voted to support medical cannabis."

"The mayor was discouraged to learn of the DEA's actions, which were in opposition to the will of the residents of this city."

Mayor Dellums has now written to Congressman John Conyers, the chairman of the House Judiciary Committee, requesting an investigation of the DEA's activities in California.

"The DEA's recent surge tactics, such as the dissemination of threatening letters to property owners and unrelenting raids that continue to place citizens in harm's way, undermine state and local authority, and jeopardize the integrity of state law," wrote Dellums to Conyer.

"We urge the House Judiciary Committee to expeditiously hold hearings and examine this very important issue."

Bruce Mirken, communications director for the Marijuana Policy Project, described the DEA's actions as 'outrageous' and 'damaging.'

"They're trying basically to get landlords to do their dirty work," said Mirken.

"They don't have enough agents to close down the dispensaries and they're trying to get landlords to do it for them."

"The wheels don't turn in Washington DC as fast as we would like them to."

"But this does appear to have gotten Chairman Conyers' attention -- and that's a good first step."

In the face of growing opposition, the DEA are unapologetic about their targeting of cannabis dispensaries in California

The dispensaries contravene federal law, but are legal under California state law, a situation that has led Dellums to speak out.

"The DEA San Francisco Field Division Office has sent out letters as a courtesy to the landowners to inform them of the suspected marijuana distribution center operating on their property," said Javier Pena, DEA Special Agent in Charge.

"The DEA is committed to enforcing our nation's drug laws and will continue to work to keep our neighborhood communities safe from drugs and the negative ripple effects they cause."