California 490.5.
(f) (1) A merchant may detain a person for a reasonable time for the purpose of conducting an investigation in a reasonable manner whenever the merchant has probable cause to believe the person to be detained is attempting to unlawfully take or has unlawfully taken merchandise from the merchant's premises.
(2) In making the detention a merchant, theater owner, or a person employed by a library facility may use a reasonable amount of nondeadly force necessary to protect himself or herself and to prevent escape of the person detained or the loss of tangible or intangible property.
(3) During the period of detention any items which a merchant.. has probable cause to believe are unlawfully taken from the premises of the merchant.. and which are in plain view may be examined by the merchant.. for the purposes of ascertaining the ownership thereof.
(4) A merchant, theater owner, a person employed by a library facility, or an agent thereof, having probable cause to believe the person detained was attempting to unlawfully take or has taken any item from the premises, or was attempting to operate a video recording device within the premises of a motion picture theater without the authority of the owner of the theater, may request the person detained to voluntarily surrender the item or recording. Should the person detained refuse to surrender the recording or item of which there is probable cause to believe has been recorded on or unlawfully taken from the premises, or attempted to be recorded or unlawfully taken from the premises, a limited and reasonable search may be conducted by those authorized to make the detention in order to recover the item. Only packages, shopping bags, handbags or other property in the immediate possession of the person detained, but not
including any clothing worn by the person, may be searched pursuant to this subdivision. Upon surrender or discovery of the item, the person detained may also be requested, but may not be required, to provide adequate proof of his or her true identity.
(6) A peace officer who accepts custody of a person arrested for an offense contained in this section may, subsequent to the arrest, search the person arrested and his or her immediate possessions for any item or items alleged to have been taken.
(7) In any civil action brought by any person resulting from a detention or arrest by a merchant, it shall be a defense to such action that the merchant detaining or arresting such person had probable cause to believe that the person had stolen or attempted to steal merchandise and that the merchant acted reasonably under all the circumstances.