The Sale of Good Act of 1979 (amended) states that if a product is unsatisfactory, that you can demand a replacement, refund, or credit be given to you if you have the receipt. This usually applies in a reasonable amount of time. Basically, if a customer doesn't like your product they can come back within 30 days with their receipt and get their money back regardless of your store's specific policy. Now that's good and all if you're in the UK, but is there any sort of commercial law that protects US citizens the same way?
I'm not aware of a specific US law that provides a refund policy like this. There are laws to protect consumers who purchase things from in-home salesmen, but I don't know of anything for retail establishments.