California Code, Military and Veterans Code - MVC § 1652

Any peace officer or any person employed as a security guard or in a supervisory capacity on premises posted pursuant to Section 1650 may stop any person found on the premises and may detain that person for the purpose of demanding their name, address, and the reason for the person's presence. If the peace officer or employee has reason to believe that the person has no right to be on the premises, they may arrest the person without a warrant on the charge of violating Section 1651.