Current european standards are laxer, especially when it comes to diesel. In fact, the whole thing was busted because a european supporter of cleaner diesel thought "look they've got much cleaner figures in the US market so they know how to do it and we can way tighten emission standards".

Then they went to road-test US-market cars, and found out the real-world emission profile was more or less identical to the EU one, and completely out of spec for the US regulations.

See http://www.bloomberg.com/news/articles/2015-09-19/volkswagen... for a timeline and a rundown with names and all.