S.C. Code Ann. § 9-1-570: Option of state employees required to become members of Federal Railroad Retirement System.

Any person who becomes an employee of the State and, because of the nature of his employment, is required to become a member of the Federal Railroad Retirement System, may elect to become, or not to become, a member of the South Carolina Retirement System, provided that such option is exercised within thirty days after he enters upon the discharge of the duties of such position.