California Code, Revenue and Taxation Code - RTC § 19556

(a) The Franchise Tax Board may disclose to persons described in paragraphs (1) to (4), inclusive, tax return and return information solely for use in an action or proceeding affecting the personnel rights of an employee or former employee, or in preparation of the action or proceeding, but only to the extent the Franchise Tax Board determines that the return or return information is, or may be, relevant and material to the action or proceeding. Tax return and return information may be disclosed pursuant to this section to any of the following persons:

(b) For purposes of this section, an action or proceeding affecting the personnel rights of an employee or former employee of the Franchise Tax Board means an action proceeding arising under either of the following:

(c) Any unauthorized disclosure by a person described in paragraphs (1) to (4), inclusive, of subdivision (a) of any tax return or return information disclosed to that person pursuant to this section shall be subject to criminal penalty and civil liability under this part for that unauthorized disclosure.