The proper legal resolution would be refunding the customer and then settle it between Amazon and the author that didn't have the rights to sell what they sold. If I buy some food at the grocery store and there's a recall due to for example contamination, I can go back to the store and get a refund. I can even go to any store selling the same item without an invoice and get a refund (for their list price I think). This is at least the deal in Denmark. This should be the same if something was sold with a missing license or improper license (if it is sold as a product but the license the seller has expires and is not renewed)