I am quite sure that this will be a horrible week for me, but thank you anyway! I wish you a far more pleasant week! :-D
Yeah there are rules, but let's be honest, very less players really check them out in the beginning. When you registered on this forum, have you read all the conditions carefully that you accepted during the registration process?! ;-)
I usually say that most rules are self-explaining like everyone should know not to teamkill or block his mates, so I usually don't require warnings on such ban requests.
However while I love fair play many others just like to win/survive and therefore camp and the place that looks most secure to them. And there are sadly several maps with places where zombies have no chance to ever reach you unless you make a big mistake and those spots are not forbidden yet. So for some players it might not be obvious that camping on the roof is forbidden unless they got told or check the rules.