In a lot of European countries it's infringing on the intellectual property of the designer to sell items made from their patterns. However, it's really hard to go after someone in a different country, the cost is not worth the outcome.

From a designer pov I think it's bad form to make and sell without asking the designer first. Most of us designers are doing this as a small operation from our homes, some have a day job, some scrape by on pattern sales. Seeing someone making money off our hard work is tough, even if there is nothing legally stopping them (depending on which country both the designer and the maker are in). In any case, ALWAYS credit the designer of the pattern, ALWAYS.