Section 38604 Of Chapter 8. Recreational Off-highway Vehicles From California Vehicle Code >> Division 16.5. >> Chapter 8.

. (a) A person operating a recreational off-highway vehicle shall not ride with a passenger, unless the passenger, while seated upright with his or her back against the seatback, can grasp the occupant handhold with the seatbelt and shoulder belt or safety harness properly fastened.
  (b) For purposes of this chapter, "occupant handhold" means any factory or aftermarket device grasped by an occupant to provide support and to assist in keeping arms and hands within the recreational off-highway vehicle. The steering wheel shall be considered an occupant handhold for the recreational off-highway vehicle operator.
  (c) Occupant handholds shall be designed to allow the recreational off-highway vehicle passenger to exit the vehicle without interference from the handholds.