From the
California Vehicle Code:
CVC Section 27802 States:
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.
This section of the CVC along with Section 27803 is the basis of the CA Motorcycle Helmet Law.