Is this cheating?

OK, I'm playing Day 17 of a 100 player map. I am fighting a player and last night he had a coup d'etat. He was on his last legs and I was due to finish him off today.

Now, the game admin, who is also the leader of the largest coalition in the game kicked the absent player and in his place came a member of the same alliance as the game admin. The new player immediately joins the game admin's coalition, moves his capital and is given a safe haven on a different continent by transferring a province.

In my mind, this is cheating. But can anyone tell me if it is actually against the rules?

I'm extremely annoyed, to put it politely.