Cannabis supporters fear the raids will drive patients into the criminal underworld. And the crackdown suggests calls to end the four-decade "war on drugs" have fallen on deaf ears, despite its failure to end global drug abuse.
"It would be hard to point to any public policy in the US that causes so much clear and obvious friction between the federal Government and almost a majority, population-wise, of states," argues Allen St Pierre, executive director of the National Organisation for the Reform of Marijuana Laws.
At the Cato Institute, a bastion of free markets, a conference this week on the war on drugs suggested it had failed and new policies were needed.
Senior fellow Ted Galen Carpenter argued the savagery of Mexico's drug wars, with 42,000 dead since 2006, had made the US less safe.
"If we want to substantially reduce cartel revenues we have to eliminate that black market premium.
"Depending on the drug, roughly 90 per cent of the retail price exists because the drugs are illegal."
Legalising cannabis would remove cannabis profits, said Jones. "We would be striking a larger blow at those cartels than any law enforcement effort ever could. What's our exit strategy for the war on drugs?"
The latest group to throw in the towel on prohibition are California's doctors, tired at walking a legal razor's edge between conflicting state and federal law.
The California Medical Association, which represents more than 35,000 doctors, came out last month in favour of legalising and regulating the drug; the first major medical group to take this step.
"It's an uncomfortable position for doctors," Donald Lyman, who wrote the CMA's new policy, told the Los Angeles Times.
"It is an open question whether cannabis is useful or not. [That] can only be answered once it is legalised and more research is done."
Although the drug has some risks, the law has proven "a failed health policy". California's cannabis clinics offer a reform template like that of Portugal, which decriminalised illicit drugs in 2001.
"The most important part of the Portuguese experience is it debunks the notion legalisation and decriminalisation would lead to soaring usage," says Carpenter. "That hasn't happened. That's the No 1 argument for moving away from prohibition."
He also notes that Portuguese crime rates are down.
Even if the DEA does shutter pot clinics, any victory could be pyrrhic. St Pierre believes Washington's "no quarter" stance on cannabis clashes with grassroots realities. He argues the US has crossed a Rubicon, citing more cannabis-tolerant baby boomers, a need for tax revenue in a deep recession, easy access to cannabis information via the internet and empathy towards the infirm who use the drug.
His claim is backed by recent initiatives, protests and polls. In March, 59 per cent of Los Angeles voters supported a tax on the city's 100 cannabis dispensaries.
Lawsuits defending the clinics estimate annual revenue from medical cannabis at US$1.5 billion to US$4.5 billion. California estimates annual sales tax at US$50 million to US$100 million.
But the medical marijuana law is imprecise. A California appeals court ruled last week that local authorities can ban clinics. But an effort to close 100 San Jose dispensaries last month was opposed by a 48,598-strong petition, launched by the Citizens Coalition for Patient Care and backed by the United Food and Commercial Workers union.
The medical marijuana issue has steadily moved into the mainstream since a California voters' initiative made it legal in 1996. Today, 15 other states, plus the District of Columbia, allow its sale.
"There's little doubt that, at least in the west, public opinion, and to some extent elite opinion, is moving away from the prohibition model," says Carpenter, who cites the Global Commission on Drug Policy and the Latin American Commission on Drugs and Democracy.
Last June, the commission, chaired by Brazilian ex-President Fernando Henrique Cardosa, petitioned the United Nations to end the drug war, which "criminalised tens of millions", and seek new policies. His cry resonates throughout Latin America where the insatiable US appetite for narcotics has reaped misery south of the border.
While Mexican cartels exploit emerging markets in the Middle East, Eastern Europe and the former Soviet Union , the mature US market remains dominant.
"We are living in the same building," said Mexico's President Felipe Calderon. "Our neighbour is the largest consumer of drugs in the world and everyone wants to sell him drugs through our doors and windows."
Prohibition is the cartels' ally, as it guarantees the black market bonanza. But reform is not easy.
The main obstacle appears to be an obdurate bureaucracy and timid leaders who fear being branded as "soft on drugs".
Carpenter says: "Not too many are willing to be first over the barrier and take the inevitable hostile fire that will come their way."
History offers a precedent. The US abandoned its prohibition on alcohol at the height of the Great Depression, convinced repeal would create jobs and tax revenue.
Now business leads the way, using that 21st century pop culture icon, the television reality show, with the impending US debut of Weed Wars.
It follows everyday folk at the Harbourside Health Centre in Oakland, which boasts it is the planet's largest cannabis retailer with 94,000 clients. As corporates exploit cannabis maybe politicians will find the nerve to debate drug reform.
