Black list
From Warzone Wiki
Your black list is a list of players who are forbidden from joining Open Seats in games and tournaments you create. This is useful if you don't want to play with a certain player. Players on your blacklist are also forbidden from inviting you to team ladder.
You can add players to your black list by visiting their profile page and clicking "Add this player to my black list." You can remove players from your black list on the Manage Black List page.