Americans for Safe Access (ASA), the country's largest medical marijuana advocacy organization, filed a lawsuit in federal court Thursday challenging the U.S. Department of Justice's attempt to close down medical marijuana dispensaries in California.

"Although the Obama Administration is entitled to enforce federal marijuana laws, the Tenth Amendment forbids it from using coercive tactics to commandeer the law-making functions of the State," said ASA Chief Counsel Joe Elford, who filed the lawsuit today in San Francisco's federal District Court. "This case is aimed at restoring California's sovereign and constitutional right to establish its own public health laws based on this country's federalist principles."

The use of marijuana for medical purposes is legal under California law. But the drug is still classified as a Schedule I substance under federal law, a classification reserved for dangerous drugs with no real medicinal value.

In early October, U.S. prosecutors in California threatened to seize the properties of state-licensed marijuana dispensaries if they didn't close up shop within 45 days. U.S. Attorneys in California have also threatened to target newspapers, radio stations and other media outlets that advertise for dispensaries.

The Drug Enforcement Administration (DEA) followed up on the threat by conducting an early morning raid on October 13th at Northstone Organics, a fully-licensed cultivation collective in Mendocino County.

ASA argues that the Justice Department has "instituted a policy to dismantle the medical marijuana laws of the State of California and to coerce its municipalities to pass bans on medical marijuana dispensaries."

U.S. Attorneys have sent letters to several municipalities warning them that their proposed local medical marijuana regulations would violate federal law.

The California Medical Association, the state’s largest doctor group, recently adopted a resolution to support the legalization of marijuana. The group said the discrepancy between state and federal law created an untenable situation for physicians.

And Gallup has found that Americans favor marijuana legalization now more than ever. A record-high 50 percent of Americans say the use of marijuana should be made legal, up 4 percent from last year and 14 percent from 2006.

“The Obama administration’s escalation of the ‘war on drugs’ and its attacks on state medical marijuana laws are only giving more and more Americans the opportunity to realize just how ridiculous and harmful our prohibition-based drug laws are,” said Neill Franklin, executive director of Law Enforcement Against Prohibition and a retired Baltimore narcotics cop.

“These numbers from Gallup, as well as the California Medical Association’s recent endorsement of marijuana legalization, show that momentum is on the side of reformers, so it’s no wonder the drug warriors are getting scared and ramping up their attacks.”

California Assemblymember Tom Ammiano (D) said last week that the federal government’s crackdown on medical marijuana dispensaries would cost the state millions of dollars in lost revenue.