CAL. HSC. CODE § 114295 : California Code - Section 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) 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.

(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.