Guild Wars 2

Can I either play against or be paired in a tPvP team with someone I blocked?

Not really a tech question, but the answer is yes.

Blocking someone doesn’t make it impossible for that person to be where he wants to be. Blocking someone isn’t punishment for that person, it is helping you. The person thats blocked didn’t do anything wrong (or if he/she did, you should report that person).

So yes, you can be paired or against someone you blocked in sPvP