California Code, Business and Professions Code - BPC § 17568.5

Upon the proclamation of a state of emergency resulting from an earthquake, flood, fire, riot, storm, or other natural disaster declared by the President of the United States or the Governor, or upon the declaration of a local emergency resulting from an earthquake, flood, fire, riot, storm, or other natural disaster by the executive officer of any county, city, or city and county, and for a period of 30 days following that proclamation or declaration, an owner or operator of a hotel or motel may not increase the hotel or motel's regular rates, as advertised immediately prior to the proclamation or declaration of emergency, by more than 10 percent.  This prohibition does not apply if the owner or operator can prove that the increase in price is directly attributable to additional costs imposed on it for goods or labor used in its business, to seasonal adjustments in rates that are regularly scheduled, or to previously contracted rates.