Cal. Business and Professions Code § 13410

(a) No person engaged in the business of extracting oil or gas from lands within the state, or of producing motor vehicle fuels for sale within the state, may refuse to sell to any city or county sufficient quantities of his or her motor vehicle fuels or lubricants, or both, sold during the normal course of business for the essential services provided by the city or county. (b) The board of supervisors of a county or its designated county agency, upon application for the purchase of motor vehicle fuels or lubricants, or both, to perform essential services by a city within that county, by any agency of such city or county that performs an essential service, or by any transit district created pursuant to law, may arrange for the purchase and shall apportion the purchase among all persons specified in subdivision (a) who engage in the sale of motor vehicle fuels or lubricants, or both, within that county. The board of supervisors or its designated county agency shall, to the extent possible, apportion the total purchase of the motor vehicle fuels or lubricants, or both, on the basis of the persons’ sales of that motor vehicle fuel or lubricant, or both, in the county during the most recent 90-day period for which information is available. (c) For purposes of this section, “essential services” means police, fire, health, and transportation services provided by public agencies.