Playing the Devil’s advocate: When you pay for something at the cash register, doesn’t it and the bag they put it in then become YOUR PRIVATE PROPERTY as soon as the cash is exchanged? Or does it when you walk out the door, or into their parking lot, or when you leave their parking lot?
I was in a Circuit City who had hired off duty city police in uniform to check bags. I walked out the door into the parking lot and here comes this cop wanting to look at my receipt and into my bag. I let him look, at the time I didn’t know if he was working for them or just patrolling looking for shoplifters. PISSED ME OFF royally. I complained to the city. Shortly after, I read in the paper that they couldn’t no longer wear their uniforms for off duty jobs. They must have gotten a lot of complaints.
According to the UCC a generic sale ends when the payment and the goods are exchanged. That would make it your private property.
I was in a Circuit City who had hired off duty city police in uniform to check bags.
That's an interesting one. But he still can't use his police powers unless he has a reasonable suspicion of you specifically shoplifting. However, I can see it convenient for the store when a shoplifter is caught, as he can do a real arrest right there, even chase the perp down the street if necessary. It eliminates all of the vagueness of shopkeeper's privilege -- how long can you hold him, what force can you use to hold him, etc..
I've seen a lot of grocery stores hiring off-duty officers in uniform for security, but I've never seen them doing bag checking.