Except as provided in s. 822.24 , a court of this state may not modify a child custody determination made by a court of another state unless a court of this state has jurisdiction to make an initial determination under s. 822.21(1) (a) or (b) and one of the following applies:
Wis. Stat. § 822.23
The above annotation cites to the Uniform Child Custody Jurisdiction Act, the predecessor statute to the current Uniform Child Custody Jurisdiction and Enforcement Act.
An action for legal custody commenced in Wisconsin after entry of a custody decree in California was an action to modify the California custody decree requiring Wisconsin jurisdiction and no California jurisdiction at the time of commencement. In Interest of A.E.H., 161 Wis. 2d 277, 468 N.W.2d 190 (1991).