California Vehicle Code Section 5061

(a) Notwithstanding any other provision of law, if the department permits the issuance of a special interest license plate for display on a motorcycle, the department shall not approve any design for that plate that incorporates either or both of the following: (1) Full or partial graphic designs appearing behind the license plate number configuration. (2) Symbols within the license plate number configuration. (b) Any special interest license plate issued for display on a motorcycle is subject to the same fees that are collected for the issuance and retention of special interest license plates on other vehicles.