In a July 31 ruling, California's 4th District Court of Appeals upheld the state's voter-approved medical marijuana law against a challenge from conservative county supervisors in San Diego and San Bernardino counties. Federal drug laws do not preempt California's medical marijuana law, the appeals court held in a unanimous decision.

The purpose of the federal law "is to combat recreational drug use, not to regulate a state's medical practices," wrote the 4th District Court of Appeals Associate Justice Alex McDonald.

San Diego county had filed a lawsuit against the state in 2006 challenging the validity of the state's ID card program, but also aiming to undermine the state's medical marijuana law overall. San Bernardino and Merced counties later joined the lawsuit. The recalcitrant counties lost in Superior Court that same year, and now they have lost again on appeal. (Merced County dropped out after the superior court ruling, opting instead to obey state law and implement an ID card program.)

But San Diego County supervisors are not yet prepared to heed the will of the voters. They announced on Tuesday that they would appeal the decision to the state Supreme Court.

Still, medical marijuana advocates celebrated the decision in County of San Diego v. San Diego NORML et al. as a victory for medical marijuana patients and states' rights.

"This is a huge win for medical marijuana patients, not only in California, but across the country," said Joe Elford, chief counsel for Americans for Safe Access, who argued before the appellate court on behalf of patients. "This ruling makes clear the ability of states to pass medical marijuana laws with an expectation that those laws will be upheld by local and state, if not federal, officials."