Cal. Bus. & Prof. Code § 17071.5

In all actions brought under this chapter proof of limitation of the quantity of any article or product sold or offered for sale to any one customer to a quantity less than the entire supply thereof owned or possessed by the seller or which he is otherwise authorized to sell at the place of such sale or offering for sale, together with proof that the price at which the article or product is so sold or offered for sale is in fact below its invoice or replacement cost, whichever is lower, raises a presumption of the purpose or intent to injure competitors or destroy competition. This section applies only to sales by persons conducting a retail business the principal part of which involves the resale to consumers of commodities purchased or acquired for that purpose, as distinguished from persons principally engaged in the sale to consumers of commodities of their own production or manufacture.