California Code, Health and Safety Code - HSC § 118935

(a) Every person and public agency providing transportation services for compensation, including, but not limited to, the National Railroad Passenger Corporation (Amtrak) to the extent permitted by federal law, passenger stage corporations, and local agencies that own or operate airports, shall designate and post, by signs of sufficient number and posted in locations that may be readily seen by persons within the area, a contiguous area of not less than 75 percent of any area made available by the person or public agency as a waiting room for these passengers where the smoking of tobacco is prohibited. Not more than 25 percent of any given area may be set aside for smokers.

(b) Every person or public agency subject to subdivision (a) shall also post, by sign of sufficient number and posted in locations as to be readily seen by persons within the area of any building where tickets, tokens, or other evidences that a fare has been paid for transportation services that are provided by the person or public agency, a notice that the smoking of tobacco by persons waiting in line to purchase the tickets, tokens, or other evidences that a fare has been paid is prohibited.

(c) It is unlawful for any person to smoke in an area posted pursuant to this section.