It's not just data they should be debating. If I goto Amsterdam have have some cookies from certain coffee houses, that's perfectly legal. If I jump onto a train back to Britain, the cookies contents are still in my system and I could potentially be arrested because the cookies contents are illegal in Britain.
So am I a criminal because I did something legal in one EU country ?
And yes, I know I shhould just shtay in Amshterdam jusht a big longer :-)