S.C. Code Ann. § 20-7-1000
(A) A tribunal of this State that has issued a child-support order consistent with the law of this State has and shall exercise continuing, exclusive jurisdiction to modify its child-support order if the order is the controlling order and:
(B) A tribunal of this State that has issued a child-support order consistent with the law of this State may not exercise continuing, exclusive jurisdiction to modify the order if: