Veterinarians who perform unauthorized procedures can be subject to disciplinary action by their state’s licensing board and also be on the receiving end of a lawsuit by the animal’s guardian. However, animal guardians are often required to sign a form when animals are admitted to a veterinary hospital. Sometimes these forms state that a veterinarian can perform additional procedures if the veterinarian determines such procedures are necessary for the animal. I suggest that you carefully read the form you signed. Since neutering provides health benefits and helps to curb pet overpopulation, consider that the neutering was an advantageous procedure. I hope your cat is doing well.