Cal. VEH § 21101.2

Local authorities may adopt rules and regulations by ordinance or resolution to provide that if a peace officer, as defined in Chapter 4.5 (commencing with Section 830) of Title 3 of Part 2 of the Penal Code, determines that the traffic load on a particular street or highway, or a portion thereof, is such that little or no vehicular flow is occurring and, additionally, if the peace officer finds that a significant number of vehicles are not promptly moving when an opportunity arises to do so, then the peace officer may divert vehicles, excepting public safety or emergency vehicles, from that street or highway, or portion thereof, subject to traffic congestion until such time as reasonably flowing traffic is restored.