S.C. Code Ann. § 25-1-590
Officers and enlisted men of the National Guard of South Carolina shall be retired by order of the commander-in-chief with a promotion of one grade, effective the date of retirement at the request of any officer or enlisted man upon completion of twenty or more years of honorable service in the National Guard of South Carolina, the Armed Forces of the United States, and reserve components thereof, except that the last ten years of such service must have been in the South Carolina National Guard, or in the National Guard of the United States and provided that the individual concerned was a member of the South Carolina National Guard at the time he was ordered to active duty in the National Guard of the U. S. status. But any commissioned officer holding the grade of major general shall, upon retirement, be retired in that grade; any warrant officer holding the grade of chief warrant officer shall, upon retirement, be retired in that grade; and any enlisted man holding the highest authorized enlisted grade shall, upon retirement, be retired in that grade.
Retired officers and retired enlisted men shall draw no pay or allowances except when placed on duty. They shall be subject to temporary detail by the commander-in-chief and while on such duty shall receive the same pay and allowances as officers and enlisted men of the same rank on the active list. On all occasions of duty or ceremony retired officers and enlisted men shall take rank below officers and enlisted men of the same grade on the active list.