Yes, privacy protection is an important right but so is the right of shareholders in their building to peace and quiet enjoyment of their premises and knowing who is living in their building for security purposes. We do not care what their relationship is between two peoplle or what they eat for breakfast, we do care when a "guest" or visitor is creating a disturbance by acting in an unruly fashion and threatening shareholders. From the answers I have gotten here it seems like the responsibility falls on the shareholder who owns the unit and we should take action to let her know via a lawyers' letter that these house rules are being violated and she is responsible for the behavior of her guest.