Cal. VEH § 21960

(a) The Department of Transportation and local authorities, by order, ordinance, or resolution, with respect to freeways, expressways, or designated portions thereof under their respective jurisdictions, to which vehicle access is completely or partially controlled, may prohibit or restrict the use of the freeways, expressways, or any portion thereof by pedestrians, bicycles or other nonmotorized traffic or by any person operating a motor-driven cycle, motorized bicycle, motorized scooter, or electrically motorized board. A prohibition or restriction pertaining to bicycles, motor-driven cycles, motorized scooters, or electrically motorized boards shall be deemed to include motorized bicycles. A person shall not operate a motorized bicycle wherever that prohibition or restriction is in force. Notwithstanding any order, ordinance, or resolution to the contrary, the driver or passengers of a disabled vehicle stopped on a freeway or expressway may walk to the nearest exit, in either direction, on that side of the freeway or expressway upon which the vehicle is disabled, from which telephone or motor vehicle repair services are available.

(b) The prohibitory regulation authorized by subdivision (a) shall be effective when appropriate signs giving notice thereof are erected upon any freeway or expressway and the approaches thereto. If any portion of a county freeway or expressway is contained within the limits of a city within the county, the county may erect signs on that portion as required under this subdivision if the ordinance has been approved by the city pursuant to subdivision (b) of Section 1730 of the Streets and Highways Code.

(c) No ordinance or resolution of local authorities shall apply to any state highway until the proposed ordinance or resolution has been presented to, and approved in writing by, the Department of Transportation.

(d) An ordinance or resolution adopted under this section on or after January 1, 2005, to prohibit pedestrian access to a county freeway or expressway shall not be effective unless it is supported by a finding by the local authority that the freeway or expressway does not have pedestrian facilities and pedestrian use would pose a safety risk to the pedestrian.