Sony recently sued several retailers who were selling imported PSPs in the UK. Sony's not happy because the PSP hasn't been officially released in Europe yet.
These unauthorized sales are called 'parallel importing"? or 'grey marketing"?, and each country deals with them differently.
The starting point is usually the doctrine of 'first sale"? or 'exhaustion"?. Under this doctrine, if the products are genuine and were sold by the manufacturer (or with the consent of the manufacturer) in another country, then the manufacturer is out of luck. However, (at least in Canada) the manufacturer can stop the importation if the imported products are materially different from the products sold in Canada.
Fortunately for Sony, it appears that UK law may be less restrictive manufacturers might be able to stop any grey marketing if the products were originally sold in countriesoutsidethe EU (although EU law doesn't appear to provide any protection if the imported products were originally sold in one of the other countries insidethe EU).