Cal. Pub. Util. Code § 99509

(a) Notwithstanding Section 99505, any person required to pay a license tax under Section 7351 of the Revenue and Taxation Code shall also collect the tax imposed under this chapter from any person to whom he sells or distributes motor vehicle fuel and shall pay such tax also for all such fuel that he uses.
Any person paying the tax who, in turn, sells or distributes such fuel to another, whether or not for use, shall include the tax as part of the selling price of the fuel. Any person thereafter who pays a price for the fuel, which includes an increment for the tax, and who subsequently resells the fuel shall include the increment so paid as part of the selling price of the fuel.
(b) Subdivision (a) of this section shall become operative only if a ruling of a federal agency becomes effective which precludes the tax imposed under this chapter on motor vehicle fuel from being included in the price charged by distributors to retailers or other persons, or precludes the increment of any price paid to the distributors that represents the tax imposed from being included in the price charged by retailers or other persons upon resale of the motor vehicle fuel, and, in such case, this subdivision shall become operative at the same time as such ruling becomes effective.