The Supreme Court won't hear another challenge to California's decade-old law permitting marijuana use for medical purposes.

The high court on Monday refused to hear appeals from San Diego and San Bernardino counties, which say the justices have never directly ruled on whether California's law trumps the federal controlled substances laws.

Supporters say marijuana helps chronically ill patients relieve pain. Critics say the drug has no medical benefit and all use should be illegal.

San Diego supervisors had sued to overturn the state law after it was approved by voters in 1996, but lower courts have ruled against them.

San Diego and San Bernardino counties argued that issuing identification cards to eligible users, as required by the 1996 state law, would violate federal law, which does not recognize the state measure.

A federal appeals court ruled that ID card laws "do not pose a significant impediment" to the federal Controlled Substances Act because that law is designed to "combat recreational drug use, not to regulate a state's medical practices."

The cases are County of San Bernardino v. California, 08-897 and County of San Diego v. San Diego NORML, 08-887.