California Code, Vehicle Code - VEH § 27360.5

(a) A parent, legal guardian, or driver shall not transport on a highway in a motor vehicle, as defined in paragraph (1) of subdivision (c) of Section 27315, a child or ward who is eight years of age or older, but less than 16 years of age, without properly securing that child or ward in an appropriate child passenger restraint system or safety belt meeting applicable federal motor vehicle safety standards.

(b) Subdivision (a) does not apply to a driver if the parent or legal guardian of the child is also present in the motor vehicle and is not the driver.