California Code, Vehicle Code - VEH § 2814.1

(a) A board of supervisors of a county may, by ordinance, establish, on highways under its jurisdiction, a vehicle inspection checkpoint program to check for violations of Sections 27153 and 27153.5. The program shall be conducted by the local agency or department with the primary responsibility for traffic law enforcement.

(b) A driver of a motor vehicle shall stop and submit to an inspection conducted under subdivision (a) when signs and displays are posted requiring that stop.

(c) A county that elects to conduct the program described under subdivision (a) may fund that program through fine proceeds deposited with the county under Section 1463.15 of the Penal Code.

(d) State and local law enforcement agencies shall not conduct motorcycle only checkpoints.