> Under Article 5(3) of 2002/58/EC YouTube are legally obligated to obtain consent before storing or accessing information already stored on an end user's terminal equipment unless it is strictly necessary for the provisions of the requested service.

What information do you have that confirms YouTube is "storing or accessing" information as a requirement of their Adblock detection? Do you think they can see your Adblock extension? That's ridiculous. The most sensible way of handling this is tracking user sessions server side to see if they downloaded the ad videos. If the ad video didn't get downloaded, you're blocking ads. No violation of this law then.