This is a problem for U.S. vendors like Amazon and Barnes & Nobel taht can not sell electronic documents to users that do not have a U.S. Credit Card, U.S. Address, and accessing the electronic store through a U.S. IP service.
"For most of our products you can choose to order from our US Shopping Cart or our UK Shopping Cart. If you live in the UK, Europe, Middle East or Africa the UK Shopping Cart may provide you with better shipping rates. As you browse our product pages, just click the "Add to Cart" or "Add to UK Cart" button. When you are done shopping, review the items in your shopping cart, make any necessary changes, and complete the ordering process. The complete list on oreilly.com includes a alphabetical list of products."