Section 38503 Of Chapter 7. All-terrain Vehicles From California Vehicle Code >> Division 16.5. >> Chapter 7.

. No person under the age of 18 years, on and after January 1, 1990, shall operate an all-terrain vehicle on public lands of this state unless the person satisfies one of the following conditions:
  (a) The person is taking a prescribed safety training course under the direct supervision of a certified all-terrain vehicle safety instructor.
  (b) The person is under the direct supervision of an adult who has in their possession an appropriate safety certificate issued by this state, or issued under the authority of another state.
  (c) The person has in possession an appropriate safety certificate issued by this state or issued under the authority of another state.