Re: Son's Girlfriend Wants to Move
You cannot prevent her from moving before the baby is born because there is no legal father yet and he cannot restrict her actions. If she has not established residency in Florida by the time the child is born, your son can attempt to file a custody action in Wisconsin and ask the child be returned to Wisconsin. If she contests jurisdiction, it will be up to the courts to determine who has jurisdiction.
If she is in Florida long enough to establish residency, it is likely Florida will have jurisdiction and there isn't a lot your son can do to demand the child be returned to Wisconsin. All he can do is seek a visitation schedule which, for the first year, at least, will likely involve him going to Florida to see his child.
I am not an attorney and any advice is not to be construed as legal advice. You might even want to ignore my advice. Actually, there are plenty of real attorneys that you might want to ignore as well.