Cal. Health and Safety Code § 114295

(a) Except as specified in subdivision (b), all mobile food facilities shall operate in conjunction with a commissary, mobile support unit, or other facility approved by the enforcement agency. (b) (1) This section does not apply to mobile food facilities that operate at community events as defined in Section 113755 and that remain in a fixed position during food preparation and its hours of operation, if potable water and liquid waste disposal facilities are available to mobile food facilities requiring potable water. (2) This section does not apply to mobile food facilities that are certified mobile farmers’ markets, as defined in Section 113743, that only sell whole fruit and vegetables, cottage food products, and prepackaged nonpotentially hazardous foods. (c) Mobile food facilities shall be stored at or within a commissary or other location approved by the enforcement agency in order to have protection from unsanitary conditions. (d) Mobile support units shall be operated from and stored at a designated commissary and shall be subject to permitting and plan review. (e) Notwithstanding any other provisions of this section, a mobile food facility that is engaged in food preparation, other than limited food preparation, as defined in Section 113818, shall not operate in conjunction with a mobile support unit.