S.C. Code Ann. § 3-3-120

A lot, not to exceed five acres, in the City of Charleston has been ceded to the United States for the erection of a customhouse. Such lot and the buildings erected thereon shall be exempt from any tax to be paid to this State. But all process, civil or criminal, issued under the authority of this State or any officer thereof shall and may be served and executed on any part of such land and on any person there being and implicated in matters of law.