Cal. Civ. Code § 1670.9
(d) A city, county, city and county, or public agency shall not, on and after January 1, 2018, approve or sign a deed, instrument, or other document related to a conveyance of land or issue a permit for the building or reuse of existing buildings by any private corporation, contractor, or vendor to house or detain noncitizens for purposes of civil immigration proceedings unless the city, county, city and county, or public agency has done both of the following: