Cal. Veh. Code § 21111
Local authorities may adopt rules and regulations by ordinance or resolution regulating vehicular traffic on privately owned and maintained roads or ways within the boundaries of any housing project or within the site of any housing owned or operated by a housing authority created under and by virtue of the Housing Authorities Law, commencing at Section 34200 of the Health and Safety Code, on privately owned and maintained roads or ways within areas which would be a residence district if the road or way were a public highway, or, with the consent of the owner, on publicly owned and maintained roads and ways within areas which are not owned by such local authorities. The rules or regulations shall not be effective until appropriate signs giving notice thereof are posted along the roads or ways affected.
Ca. Veh. Code § 21111