Cal. Vehicle Code - VEH § 28085. Section 28085.
Any motor vehicle may be equipped with a theft alarm system which flashes the lights of the vehicle, or sounds an audible signal, or both, and which operates as follows:
(a)
The system may flash any of the lights required or permitted on the vehicle.
(b)
The system may sound an audible signal.
(c)
No vehicle shall be equipped with a theft alarm system which emits the
sound of a siren.