Possibilty to ban players from joining alliance?


Would like to have the option to ban a player (his account) from our alliance.
Had a player join who turned out to be a bit of a stalker/creep… who wanted to create drama. He got removed but a few days later he rejoined under another name. Trying to go un-noticed.
We figured out who it was and booted him, but would like to prevent him trying to join again under a new name… to block his account… is this possible?.
Im sure there are loads of players like this out there which make the game unpleasant. And a block feature might be worth looking into.