California Code, Health and Safety Code - HSC § 43210

(a) The state board shall provide, by regulation, for the testing of motor vehicles on factory assembly lines or in a manner which the state board determines best suited to carry out the purpose of this part and this section.

(b) If a motor vehicle does not meet the prescribed assembly line standards, the motor vehicle may be retested according to the official test procedures upon which original certification for that make and model vehicle was based. Any motor vehicle meeting the applicable emission standards by either of the testing procedures shall be deemed to meet the emission standards of the State of California and shall be eligible for sale in this state.

(c) The regulations adopted by the state board pursuant to subdivision (a) shall provide for reduced, statistically valid testing of motor vehicles contained in large engine families and for which initial test results indicate compliance with the applicable standards.