I suppose you have to use your TOS for that. (In fact, a banner that tells European users that they aren't allowed to use your site is probably the easiest way

I suppose you have to use your TOS for that. (In fact, a banner that tells European users that they aren't allowed to use your site is probably the easiest way to insulate yourself -- if you collect their data because they used your service illegally, I'm not sure you can be blamed.)