California Code, Vehicle Code - VEH § 21118

(a) A local authority may adopt rules and regulations by ordinance or resolution to restrict the routes or streets upon which a tour bus described in subdivision (b) of Section 612 may be operated, if the local authority determines that it is unsafe to operate those vehicles on those routes or streets.

(b) A local authority may adopt rules and regulations by ordinance or resolution to prohibit the use of loudspeakers or public address systems by a tour bus described in subdivision (b) of Section 612, and instead require the use of headphones or similar devices by passengers for any information or presentation provided for the passengers.