Oy! Referee!

Just like in real wars, there's a referee that tries to break it up when things start to get rough. And just like in real wars both sides turn on him and obliterate him before going back to killing each other.
Only kidding! Referees can't actually do anything except move around. They're there so players know that a moderator is keeping an eye on them. They're also very useful for checking AI behaviour without getting attacked!