Cal. Rev. & Tax. Code § 9255

It is unlawful for the board or any person having an administrative duty under this part to make known in any manner whatever the business affairs, operations, or information obtained by an investigation of records and equipment of any user visited or examined in the discharge of official duty, or the amount or source of income, profits, losses, expenditures, or any particular thereof set forth or disclosed in any return, or to permit any return or copy thereof or any book containing any abstract or particulars thereof to be seen or examined by any person except to another government, state agency or federal agency as specified in Section 9255.1. Information respecting the tax due from a user may be furnished, however, to any person owning or having an interest in a motor vehicle subject to the lien of the tax. The Governor may, by general or special order, authorize examination by other state officers, by tax officers of another state, by the federal government, if a reciprocal arrangement exists, or by any other person of the records maintained by the board under this part. The information so obtained pursuant to the order of the Governor shall not be made public except to the extent and in the manner that the order may authorize that it be made public. Successors, receivers, trustees, executors, administrators, assignees, and guarantors, if directly interested, may be given information as to the items included in the measure and amounts of any unpaid tax or amounts of tax required to be collected, interest and penalties.

Any violation of this section is a misdemeanor and is punishable by a fine not exceeding one thousand dollars ($1,000), by imprisonment not exceeding one year, or by both that fine and imprisonment, in the discretion of the court.