Cal. Food & Agric. Code § 19362

Every restaurant, cafe, or other public eating place offering or serving horsemeat for human consumption shall have stamped on all menus, in green ink letters not less than one-half inch in height and one-quarter inch in width the words “horsemeat served here”; likewise a placard must be prominently displayed bearing the words “horsemeat served here” in letters not less than four inches in height and one-half inch in width.