The law (in general) for shoplifting is, you have to be challenged outside the shop AFTER you have exited. However, last night I had stopped to read the headlines of a newspaper by the door when the alarm went off - it was one of those security tag detectors - it was somebody coming IN! A member of staff went across to them and asked to look in there bag, explaining that it was probably something in there that had set the alarm off. The question is, what would the position be if the people had refused to allow the member of staff to look in their bag? Can the shop people insist on looking, or would they have to call the police? This has happened to me, I have brought something (non food) in another shop and set off the alarm in this supermarket, but nobody has bothered me - because I was coming in?