The statute (767.481) requires 60 days written notice by certified mail of the intent to move. The notice must include the proposed action, including the specific date and location of the move. You should also state the reason and, although not required, the proposed alternative placement. If she objects, she must notify you and file it with the court system. The court will then order mediation. If she doesn't object, he can move his daughter.
However, there are certain other rules in place because he is active military. If Mom objects, he should contact his JAG office for advice. He should also retain local counsel. However, if Mom hasn't seen the daughter in a year, it is unlikely that the court would prevent him from moving with his daughter given the circumstances.
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