S.C. Code § 44-27-20
An order of a court of competent jurisdiction of another state or of the District of Columbia authorizing admittance of an individual by any agency of the United States shall have the same force and effect as to the individual while in this State as in the jurisdiction in which is situated the court entering the order, and such court shall be deemed to have retained jurisdiction of the individual admitted for the purpose of inquiring into his mental condition and of determining the necessity for continuance of his confinement. Consent is hereby given to the application of the law of the state or district in which is located the court issuing the order for admittance with respect to the authority of the superintendent of any hospital or institution operated in this State by any agency of the United States to retain custody, transfer, conditionally discharge or discharge the individual confined.
S.C. Code § 44-27-20