Wis. Stat. § 48.15: Jurisdiction of other courts to determine legal custody.

Except as provided in ss. 48.028 (3) and 48.9795 (2) (b) 2., nothing in this chapter deprives another court of the right to determine the legal custody of a child by habeas corpus or to determine the legal custody or guardianship of a child if the legal custody or guardianship is incidental to the determination of an action pending in that court. Except as provided in s. 48.028 (3), the jurisdiction of the court assigned to exercise jurisdiction under this chapter and ch. 938 is paramount in all cases involving children alleged to come within the provisions of ss. 48.13 and 48.14 and unborn children and their expectant mothers alleged to come within the provisions of ss. 48.133 and 48.14 (5).