Cal. Public Utilities Code § 27292

Any time after the defeat of a bond issue by the voters of the district any city or unincorporated territory, a majority of whose voters voting on a district bond issue proposition voted against said proposition, may be excluded by order of the board upon receipt by the board of a verified petition of ten percent (10%) of the total vote cast in the territory proposed to be excluded, or of a resolution adopted by the city council or board of supervisors having jurisdiction of the territory. However, no city shall be divided and not less than one-half of the territory under the jurisdiction of the board of supervisors and then remaining within the district shall be included in any petition or resolution or combination thereof filed simultaneously, nor shall any territory be excluded by any petition or resolution or combination thereof which creates areas of noncontiguous territory or will be entirely surrounded by the remainder of the district.