California Code, Vehicle Code - VEH § 12501

(a) An officer or employee of the United States, while operating a motor vehicle owned or controlled by the United States on the business of the United States, except when the motor vehicle being operated is a commercial motor vehicle, as defined in Section 15210.

(b) Any person while driving or operating implements of husbandry incidentally operated or moved over a highway, except as provided in Section 36300 or 36305.

(c) Any person driving or operating an off-highway motor vehicle subject to identification, as defined in Section 38012, while driving or operating such motor vehicle as provided in Section 38025. Nothing in this subdivision authorizes operation of a motor vehicle by a person without a valid driver's license upon any offstreet parking facility, as defined in subdivision (c) of Section 12500.