California Code, Health and Safety Code - HSC § 121935

(a) No person shall take a sentry dog or a tracker or attack dog into, or keep a sentry dog or a tracker or attack dog in, any portion of any business establishment that is open to the general public, unless any such dog is accompanied or kept by a dog handler.

(b) No person shall keep any sentry dog or tracker or attack dog in any business establishment or any other place open to the general public at any time unless there is posted at every entrance of the business establishment or place a sign of sufficient size and design to warn persons that such a dog is used at the business establishment or place.

(c) This section does not apply to dogs used and accompanied by peace officers or uniformed employees of private patrol operators and operators of a private patrol service who are licensed pursuant to Chapter 11.5 (commencing with Section 7580) of Division 3 of the Business and Professions Code, while employees are acting within the course and scope of their employment as private patrolmen.

(d) This section does not apply to any dog handler or his or her dog while training the dog or another dog handler.