You might want to look as well:

"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."

Probable cause required. It is not probable cause to say, "the person is leaving the store with a bag, so I'm going to detain the person and search the bag."