Check these two listings both from BD.uk:
http://www.bookdepository.co.uk/book...Under-the-Dome
http://www.bookdepository.co.uk/book...Under-the-Dome
If the p.o. sales argument were valid one of these listings would be "illegal"
As a funny fact Amazon.com has both editions (UK and US) for sale too, but the Uk is marked as "collector" and with the wrong publisher (the ISBN shows clearly is the UK edition) and sold at a higher price; maybe someone should point to them the inconsistency in how they treat books vs ebooks as point of sale goes...