Cal. Rev. & Tax. Code § 60608

(a) Upon request from the officials to whom is entrusted the enforcement of the motor fuel tax laws of another government, the board may furnish to those officials the information in the possession of the board that is deemed essential to the enforcement of the motor fuel tax laws.
Any information so furnished shall not be used for any purpose other than that for which it was furnished.
(b) The board may furnish to any state or federal agency investigating violations of or enforcing any state or federal law related to motor fuels any motor fuel information in the possession of the board that is deemed necessary for the enforcement of those laws.
(c) The board may furnish any interstate user information obtained by the board under this part to any state or federal agency for use by that agency in the enforcement of interstate user registration or licensing laws, or interstate vehicle registration or licensing laws.