The Arizona Supreme Court is letting stand a lower court's ruling that the state's medical marijuana law is constitutional in requiring counties to approve reasonable zoning regulations.

Maricopa County Attorney Bill Montgomery had appealed a Court of Appeals ruling last December that rejected his argument that the state medical marijuana law is pre-empted by the federal Controlled Substances Act.

That federal law still makes marijuana illegal. The case in the appeal decided by the appeals court started with a legal dispute over whether Maricopa County officials had to approve zoning for a medical marijuana dispensary in Sun City.

Montgomery argued that allowing Arizona's medical marijuana program to stand despite the federal law undermines federalism and the "fundamental principle of the rule of law."