The White House said it expects those kinds of raids to end once Mr. Obama nominates someone to take charge of DEA, which is still run by Bush administration holdovers.
“The president believes that federal resources should not be used to circumvent state laws, and as he continues to appoint senior leadership to fill out the ranks of the federal government, he expects them to review their policies with that in mind," White House spokesman Nick Shapiro said.
Medical use of marijuana is legal under the law in California and a dozen other states, but the federal government under President Bush, bolstered by a 2005 Supreme Court ruling, argued that federal interests trumped state law.
Dogged by marijuana advocates throughout the campaign, Mr. Obama repeatedly said he was opposed to using the federal government to raid medical marijuana shops, particularly because it was an infringement on states' decisions.
“I'm not going to be using Justice Department resources to try to circumvent state laws on this issue," Mr. Obama told the Mail Tribune newspaper in Oregon in March, during the Democratic primary campaign.
He told the newspaper the "basic concept of using medical marijuana for the same purposes and with the same controls as other drugs prescribed by doctors, I think that's entirely appropriate."
Mr. Obama is still filling key law enforcement posts. For now, DEA is run by acting Administrator Michele Leonhart, a Bush appointee.
Special Agent Sarah Pullen of the DEA's Los Angeles office said agents raided four marijuana dispensaries about noon Tuesday. Two were in Venice and one each was in Marina Del Rey and Playa Del Ray -- all in the Los Angeles area.
A man who answered the phone at Marina Caregivers in Marina Del Rey said his shop was the target of a raid but declined to elaborate, saying the shop was just trying to get back to operating.
Agent Pullen said the four raids seized $10,000 in cash and 224 kilograms of marijuana and marijuana-laced food, such as cookies. No one was arrested, she said, but the raid is part of an ongoing investigation seeking to trace the marijuana back to its suppliers or source.
She said agents have conducted 30 or 40 similar raids in the past several years, many of which resulted in prosecutions.
"It's clear that the DEA is showing no respect for President Obama's campaign promises," said Dan Bernath, a spokesman for the Marijuana Policy Project in Washington, which advocates for medical marijuana and for decriminalizing the drug.
California allows patients whose doctors prescribe marijuana to use the drug. The state has set up a registry to allow patients to obtain cards allowing them to possess, grow, transport and use marijuana.
Kris Hermes of Americans for Safe Access, a medical marijuana advocacy group in California, called the raids an attempt to undermine state law and said they were apparently conducted without the knowledge of Los Angeles city or police officials.
He said the DEA has raided five medical marijuana dispensaries in the state since Mr. Obama was inaugurated and that the first took place on Jan. 22 in South Lake Tahoe.
"President Obama needs to keep a promise he made, not just in one campaign stop, but in multiple speeches that he would not be spending Justice Department funds on these kinds of raids," Mr. Hermes said. "We do want to give him a little bit of leeway, but at the same time we're expecting him to stop this egregious enforcement policy that is continuing into his presidency."
He said he is aware that Mr. Obama has not installed his own DEA chief but that new Attorney General "Eric Holder can still suspend these types of operations."
The Justice Department referred questions to the White House.