California Code, Food and Agricultural Code (Formerly Agricultural Code) - FAC § 5344

(a) It is unlawful for the operator of any vehicle to fail to stop the vehicle at an inspection station or to willfully avoid an inspection station. It is also unlawful for the operator to fail to stop either upon demand of a clearly identified plant quarantine officer or upon demand of an officer of the California Highway Patrol, when the officer orders the operator to stop for the purpose of determining whether any quarantine which is established pursuant to any provision of this division is being violated.

(b) Notwithstanding Section 5309, a violation of this section is a misdemeanor and grounds for the vehicle to be stopped for inspection.