S.C. Code Ann. § 11-43-400

Subsequent amendments to this article may not limit the rights vested in the bank with respect to any agreements made with, or remedies available to, the holders of bonds issued under this article before the enactment of the amendments until the bonds, with all premiums and interest on them, and all costs and expenses in connection with any proceeding by or on behalf of the holders, are fully met and discharged.