Many shelters include provisions in their adoption agreements requiring the adopter to return an adopted animal to the shelter if the adopter no longer wants to keep the animal. This type of provision is included so that the shelter can better ensure the animal’s well-being. However, I have found that some shelters will not enforce such a provision once the shelter is satisfied that the animal is in a good home. In such instances, shelters will change their records to include the new adopter’s information. If the shelter wants to pursue the new adoption fee and the "new" adopter does not want to pay the fee, the shelter can commence a legal action and try to recoup the money that way. I do not think it is common for shelters to take this kind of action. However, consider that shelters spend a lot of money to care for homeless animals, and that giving a donation to help them help more animals may resolve your situation and provide closure.