Legal Question in Family Law in California

(S)he needs to have custody and visitation worked out before they leave and bring this before the court for the judge to issue as an order, or else (s)he is going to have to find a way to remain in compliance with the current order. If (s)he says (s)he wants to leave without working something out that you are satisfied with, this is what an ex parte request is allowed to address. This will allow you to shorten the time for notice to prevent the child from being removed from the court's jurisdiction.

It depends on if you mean temporarily or permenantly. If you mean a move away, then Ms. Ellifritz' answer is correct. If you mean temporarily, then yes they can unless there is an order against it.