Pet custody in Illinois used to be a relatively simple thing. The court would look at the pet or pets as marital property and divide it accordingly.Contact a Chicago pet custody lawyer from Arnoux Sharma Standeford, LLC to learn more about pet custody in a divorce. A postnuptial agreement can specify an adopted or purchased animal belongs to one individual only. Illinois has taken steps to recognize this concept and has put rules into place on how to handle custody of pets after a divorce. Beginning this year, Illinois judges will no longer treat pets like property during a divorce, but will rather treat them as members of your family. Pet Custody Agreement. The Easiest Way to Add e-Signatures. You sold your dog with no contract, so you have no right to "repossess" the dog. The law now allows for joint custody in a divorce, and states that the court "shall take into consideration the well-being of the companion animal."