I remember reading once Ajax saying that if you had a normal ticket and couldn't prove you were a Dutch resident you could be refused entry. I'm surprised this doesn't contravene EU law.
Really? I'm not so sure about this. Maybe a membership card (which you don't need to be a Dutch resident for necessarily) for certain games, for example, Feyenoord. With these games you need to bring ID alongside the membership card which is a prevention against crowd trouble.