S.C. Code Ann. § 44-27-10

When the individual is admitted to any institution operated by any agency of the United States within or without this State, he shall be subject to the rules and regulations of the agency. The superintendent of any institution operated by the agency and in which the individual is confined shall, with respect to the individual, be vested with the same powers as the superintendents of institutions or the Office of Mental Health within this State with respect to detention, custody, transfer, conditional discharge or discharge of patients.