Uhhhh the "shopkeepers privilege" is well established in common law and most states have a version of it. But I've never seen one that says they have a right to inspect. The right allows you to detain when there is probable cause or reasonable suspicion.
You are allowed to call the police yourself, and should, you are allowed to request criminal charges be filed for illegal restraint, you are allowed to defend your person should they get stupid about forcing you to do things that they are not allowed to do. You are allowed to raise your voice and loudly proclaim your innocence in a manner that causes them great embarrassment. You are allowed to leave if the police to not arrive in a timely manner. You are allowed to sue the store and the people involved. You are allowed to broadcast what happened to the media and on the Internet.
The key here is your innocence. You had damn well better be before you do any or all of the above.
The real issue is the lack of professional loss protection bubbas. There are very few pros, most are ex cops or wannabe cops who think they are Jack Bauer. Tell them no and they will brandish their pepper spray. BTDT. Record their hysterics and then file charges on them. If they get really stupid, esp in front of witnesses, drop them. Its easier than they realize and they will have no idea its coming BTDT2. A real pro will never risk any of the above actions unless he is absolutely sure he has some one dead to rights. If he doesn't he lets them go. The wannabes have no clue and will play super cop. When they do, destroying their lives is the correct response. They have no business being allowed in any position of authority after that.
How then can they deal with shoplifting and screening items leaving the store if they can’t look into the bag. That’s what I meant by inspect?