There are not many rules when it comes to the Guardian Tower (or the "Tower" for short) so I won't bother putting this in list form....
The number one rule is that for the Head Guardian's Office/Room, you CANNOT just randomly appear in it unless you are given permission to enter. Even if that is where you are starting, you have to have your character waiting outside of the door. Specific seals have been placed on the room so no one but the head Guardian can enter!
Another rule is that you cannot enter the cellar, that is only for teachers or Heather (she is the cook) to enter!
Lastly, you cannot hit the Tower when fighting and/or training and you aren't allowed to do either inside. They don't want anything wrecked so even if it is storming outside, if you want to train or fight, you have to do it outside. Some methods of training are allowed inside (like meditation training) that won't cause any damage to the Tower. If you do train inside the Tower and are caught by anyone (In Character, not in Real Life) and Baina is notified then you have to face your punishment.