S.C. Code Ann. § 16-7-30

Members of the South Carolina National Guard shall have the powers of peace officers when they are (1) called or ordered into active State service by the Governor pursuant to Sections 25-1-1840, 25-1-1860 and 25-1-1890, (2) serving within the area wherein military assistance is required, and (3) directly assisting civil authorities. Any person arrested or taken into custody by a member of the Guard, under the provisions of this section, shall be dealt with as required by law of peace officers. No person arrested and taken into custody, under no circumstances, shall be detained or confined at any military installation.