Amazon -> 30-day return policy, they cover shipping costs, no questions asked, doesn't matter how much you used the item.

Law -> 14-day return policy, you pay for shipping, the shop will make it as difficult as possible to let you return the item (even if it's illegal), they don't have to take the item if you opened it (which makes no sense - how do I know I don't want it if I can't try it?)