CA Veh Code 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.