S.C. Code Ann. § 11-49-160

The State pledges and agrees with the authority, and the holders of the bonds in which the authority has included such pledge and agreement, that the State shall not limit or alter the rights of the authority to fulfill the terms of its agreements with such holders, and shall not in any way impair the rights and remedies of such holders or the security for such bonds until the bonds, together with the interest on them and all costs and expenses in connection with any action or proceeding by or on behalf of such holders, are fully paid and discharged.