For the duration of their stay, all housemates must adhere to all of Big Brother's rules at all times or risk punishment. If a housemate breaks a rule the punishment could be one of varying punishments - depending on the seriousness of the rule break - ranging from being banned from using the swimming pool to being immediately ejected from the House.
If a housemate manages to break any of the first three rules, Big Brother will almost definetely choose to eject the housemate. In some minor break Big Brother will choose to issue the offending housemate with an official warning.
In more recent series Big Brother has been seen coming down harder on those who break the rule regarding nominations. Frequently, those who discuss nominations are then nominated for eviction by Big Brother.
Breaking any of the other rules can result in an official warning, but persistent rule breaking can quickly lead to ejection.