California Code, Business and Professions Code - BPC § 13530

(a) Nothing in this article applies to price indicators and signs referred to in Article 8 (commencing with Section 13470). However, any numerals designating the total price per gallon, liter, or other unit of measurement adopted pursuant to Section 12107, 13404, or 13404.5 for a particular brand and grade of motor vehicle fuel permitted or required under Article 8 (commencing with Section 13470) shall, unless otherwise stated, be identical in numerical value with the price per gallon, liter, or other unit of measurement for the same brand and grade of motor vehicle fuel permitted or required under this article.

(b) Nothing in this chapter requires that the cash or merchandise value of trading stamps be stated on any advertising media that either advertises the stamps or advertises the price of motor vehicle fuel.

(c) Unless otherwise prohibited, any person selling motor vehicle fuel by the liter shall be authorized to advertise its price by displaying on the advertising medium either the price per liter or the price per gallon.