Each store is a separate lunacy on this kind of thing, and unless you have a copy of the corporate policy that says different, you have to go by the manager's ruling. Make sure the store manager knows why you will be shopping elsewhere. If the corporate policy backs him up, be sure corporate knows why you will be shopping elsewhere. No need to get upset. Just say something like "Oh, sorry, I misunderstood," and go to WalMart. Let the store manager put the groceries back on the shelf after you leave.