Cal. VEH § 5101

Any person who is the registered owner or lessee of a passenger vehicle, commercial motor vehicle, motorcycle, trailer, or semitrailer registered or certificated with the department, or who makes application for an original registration or renewal registration of that vehicle, may, upon payment of the fee prescribed in Section 5106 and those fees required by Sections 5022 to 5024, inclusive, apply to the department for environmental license plates, in the manner prescribed in Section 5105, which plates shall be affixed to the passenger vehicle, commercial motor vehicle, motorcycle, trailer, or semitrailer for which registration is sought in lieu of the regular license plates.