California Code, Vehicle Code - VEH § 27802

(a) The department may adopt reasonable regulations establishing specifications and standards for safety helmets offered for sale, or sold, for use by drivers and passengers of motorcycles and motorized bicycles as it determines are necessary for the safety of those drivers and passengers.The regulations shall include, but are not limited to, the requirements imposed by Federal Motor Vehicle Safety Standard No. 218 (49 C.F.R. Sec. 571.218) and may include compliance with that federal standard by incorporation of its requirements by reference. Each helmet sold or offered for sale for use by drivers and passengers of motorcycles and motorized bicycles shall be conspicuously labeled in accordance with the federal standard which shall constitute the manufacturer's certification that the helmet conforms to the applicable federal motor vehicle safety standards.

(b) No person shall sell, or offer for sale, for use by a driver or passenger of a motorcycle or motorized bicycle any safety helmet which is not of a type meeting requirements established by the department.