How will pets be affected?
Once tamed into a pet, a creature becomes blue to players. A pet is treated as an independent entity until given a hostile command (attack or guard) by its owner. Once given a hostile command, the controller information for the pet is set to the owner who gave it the command and the pet is given the color and status of its controller (blue/Innocent, gray/Criminal, guild status, etc.). If another owner gives a pet a hostile command, the pet's controller information is updated to the owner who issued the last command.
If a pet is released while its controller status is set, the controller status will remain set for 2-minutes. Also, the 2-minute timer is refreshed as long as the pet is involved in combat. If the pet attacks an Innocent during this time, the controller is still responsible and will be flagged as both a Criminal and Aggressor. If the Innocent dies, the controller can be reported. If someone attacks the pet after it has been released they will become an Aggressor and the controller will not be responsible if the attacker dies.
Summoned Creatures work exactly like pets except that you will not gain any Karma or Fame if you kill them. Killing them is only good for raising skills.

What happens when I order a pet to attack someone?
Commanding a pet to attack sets you as the pet's controller. The attack is treated exactly as if you had attacked directly with the addition that your pet also inherits whatever flags you receive from the attack. In other words, if the target of the attack is an Innocent, both you and your pet will be flagged as Criminals and Aggressors. If the target is a Criminal or Murderer, both you and your pet will be flagged as Aggressors.

What happens if I kill a pet?
You can never be reported as a Murderer if you kill a pet, but if the pet was blue when you attacked, you will be flagged as a Criminal and you will lose Karma. You'll gain Fame for killing a pet.

How does pet guarding work in the new system?
Issuing the guard command sets you as the pet's controller for the duration of the guarding plus an additional 2-minutes after the pet stops guarding. Guarded items will have the word [Guarded] put over them. Using a guarded item (like a door) or taking a guarded item will flag the perpetrator as a Criminal. The pet guarding the item will automatically attack the perpetrator flagging both you and your pet as Aggressors (to the perpetrator). If the pet kills the perpetrator you cannot be reported because the perpetrator is a Criminal.

Assigning your pet to guard another player or pet works similarly depending on the status of the player or pet. If you assign your pet to guard an Innocent or a BLUE pet and someone attacks the guarded player or pet, you and your pet will be flagged as Aggressor (to the attacker) when your pet retaliates. Since the attacker will be flagged as a Criminal for attacking the Innocent or BLUE pet, you cannot be reported if your pet kills the attacker.

If you assign the pet to guard a Criminal or Murderer, and someone attacks the guarded Criminal or Murderer, you and your pet will be flagged as Aggressor (to the attacker) when your pet retaliates. If the attacker was an Innocent, you and your pet will also be flagged as Criminals and you can be reported if your pet kills the Innocent. If the attacker is a Criminal or Murderer, your pet can attack freely and neither you nor your pet will be flagged as Criminals and you will also not have to worry about being reported.

What happens if I order my pet to guard an Innocent and that person becomes a Criminal while my pet is still guarding?
Since you are still the controller, if an Innocent attacks the guarded player while the guarded player is a Criminal, you will become a Criminal and Aggressor (to the Innocent). If the Innocent dies, you can be reported.  Don't tell your pet to guard someone unless you trust them.  If you don't trust them, give them control of the pet, and let them guard themselves.

Do guarding pets only attack Aggressors to the guarded person?
No, they attack anyone who attacks the guarded person. So if you attack a Criminal or Murderer while you are being guarded, your pet will begin attacking as soon as the Criminal or Murderer defends.

What happens if someone attacks me while my pet is guarding them?
If you tell your pet to guard someone and they attack you, your pet will attack you as soon as you auto-defend. However, the pet is under your control, and you won't be flagged Criminal if something you control hurts yourself.

If my pet kills a monster will I gain Reputation?
Yes, both Karma and Fame.

What happens if I order my pet to fetch a guarded item?
Both you and your pet will be flagged as Criminals as soon as your pet takes the item.