California Code, Vehicle Code - VEH § 38285

Only those signs, signals, markings, or devices that conform to the uniform standards and specifications adopted by the Department of Parks and Recreation, with the approval of the Off-Highway Motor Vehicle Recreation Commission, shall be placed as provided in Section 38280.

Special signs, signals, markings, or devices may be used on a temporary basis for purposes of directing traffic on and at sanctioned events conducted on public lands with permission of the agency having administrative jurisdiction over such lands.