Hey everyone,
It is now possible to set a pet group to allow trade offers from people on your "friends list" only. If you add people to your "foes list", they can not send you trade offers (it will just show them the standard message that you are not accepting any trades on your pets).
You can edit your friends and foes list here:
ucp.php?i=zebra&mode=friends
The trade setting can be found at the bottom of any of your pet groups - just look for the "trading settings" link.