The Supreme Court has just refused to hear a case from two California counties that argued they shouldn't have to comply with the state's medical-marijuana law because all marijuana use is illegal at the federal level.

The case stems from a challenge in 2006, in which San Diego and San Bernardino Counties argued that they could ignore a California law that requires counties to provide identification cards to medical-marijuana patients, who are required to have a doctor's note to grow or possess pot. Seven other counties also refused to provide the cards, which essentially granted cardholders immunity from arrest if they appeared to be complying with the law. State courts decided the counties must issue the cards. But the counties thought the federal court would give deference to federal law, which makes no exception for marijuana use by sick people, over state law. But by refusing to hear the case, the Supreme Court guts the argument that local governments can ignore any state drug law that doesn't jibe with federal rules. "The courts have made clear that federal law does not preempt California's medical marijuana law and that local officials must comply with that law," Joe Elford, Chief Counsel with Americans for Safe Access, a national medical marijuana advocacy group that represented patients in the county's lawsuit against the state, said in a statement.

The question now is whether Washington state would push for a similar identification program. As it stands, a patient here must tote around a doctor's letter—which could be easily forged and police often doubt the authenticity of—to prove medical necessity to grow or possess pot. A state registry would be a mostly foolproof authentication of a patient's right to possess marijuana and could reduce arrests; however, many patients are concerned that personal data would be used by law-enforcement officers who seek to harass them.