California Code, Vehicle Code - VEH § 35719

No ordinance adopted pursuant to Section 35717 shall be effective with respect to any street, road or highway which connects with, or is a continuation of, any street, road or highway of an adjoining county unless the board of supervisors of each county in which the street, road or highway is a through highway, by concurrent action and like limitation, prohibit the use of such street, road or highway pursuant to this section.