California Code, Revenue and Taxation Code - RTC § 60702

It is unlawful for any supplier or other person to conspire with any person, firm, association, or corporation, or any officer or agent thereof, to withhold diesel fuel from export, or to divert it from interstate or foreign transit begun in this state, or to return it to this state for sale or use so as to avoid any of the taxes imposed by this part.

Each shipment illegally diverted or illegally returned constitutes a separate offense.  The unit of each shipment is the cargo of one vessel, one railroad car load, one automobile truck load, one truck and trailer load, one drum, one barrel, one case, or one can.

Any person violating any provision of this section is guilty of a misdemeanor punishable as provided in Section 60706.