As someone who works for Walmart I can tell you it doesn't stop at the express line. Customers are pretty much allowed to do anything they please. In my day it was, "if you break it, open it, use it or destroy it you bought it", "clearance sales were final" and "children weren't allowed to run about the store like it was their personal playground". Not anymore in fact customers can physically assault employees and management won't press charges...you're on your own. The world has gone to hell.