Cal. Health and Safety Code § 18928.1

Building standards adopted or approved by the commission shall incorporate the text of the model codes, applicable national specifications, or published standards, in whole or in part, only by reference, with appropriate additions or deletions therefrom. The commission may elect to adopt or approve standards which incorporate, in whole or in part, the text of these publications, with changes therein, or deletions therefrom, directly incorporated into the text of the California Building Standards Code, but no textual material contained in any of the model codes, as enumerated in Section 18916, may be included in the California Building Standards Code by means other than incorporation by reference, unless the commission and the governing body of the organization that publishes the model codes first reach a written agreement concerning the terms and conditions of the publication, including, but not limited to, whether the publication will be by the commission or the model code organization, or both. The model code governing body may not withhold any publication agreement on the basis of the substantive provisions contained in the California Building Standards Code.