YouTube’s ad blocking crackdown is facing a new challenge: privacy laws | Privacy advocates argue YouTube’s ad blocker restrictions violate the European Union’s online privacy laws.::YouTube is launching a “global effort” to crack down on ad blockers, but some privacy advocates in the European Union argue that it’s illegal.
You can. After all the GDPR does not forbid you to not accept to talk to someone.
I’m not sure that helps much. Blacklisting senders based on their IP is much more commonly (and effectively) done on intermediary servers rather than on the client.