Flying between US and EU
 

Simple straight up question but I cannot seem to find a good answer via google.

Basically do you need both FAA and JAA(or whatever the hell they have turned it into now after 30th July) approved CPL to fly for an airline from US to EU and back. Legally ;)

No. This is one of the most fundamental issues addressed by the Chicago Convention and probably in the first chapter of every air law book.

Providing your license is issued by the same state the aircraft is registered in your privileges extend worldwide. This is how UK-based private pilots can register their aircraft on the N register, in order to make use of the infinitely more sensible licensing regime and accessible FAA IR without their aircraft ever going near the USA.