(750 ILCS 36/203)
Sec. 203. Jurisdiction To Modify Determination. Except as otherwise provided in Section 204, 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 Section 201(a)(1) or (2) and:
(1) the court of the other state determines it no longer has exclusive, continuing jurisdiction under Section 202 or that a court of this State would be a more convenient forum under Section 207; or
(2) a court of this State or a court of the other state determines that the child, the child's parents, and any person acting as a parent do not presently reside in the other state. (Source: P.A. 93-108, eff. 1-1-04.)