S.C. Code Ann. § 63-15-334: Custody modification by another state.

Except as otherwise provided in Section 63-15-336, 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 63-15-330(A)(1) or (2) and:

(1) the court of the other state determines it no longer has exclusive, continuing jurisdiction under Section 63-15-332 or that a court of this State would be a more convenient forum under Section 63-15-342; 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.