Servals are legal in Florida, Mississippi, Tennessee and Texas. The big cats require a class II wildlife permit while Texas allows servals with a license called a certificate of registration. Mississippi and Tennessee allow servals with no special restrictions.
All states have laws regarding possession of wild animals, but many states do not include a list of specific animals so it is possible that other states will allow them. To confirm the right to own servals or any type of exotic animals in any state, contact that state's department of natural resources. As many as 18 states use the broader term "cats" or "wild cat'' without specifying certain types of wild cat that are legal or illegal to own.