S.C. Code Ann. § 48-37-30

When the Governor shall have executed such compact on behalf of this State and shall have caused a verified copy thereof to be filed with the Secretary of State, and when such compact shall have been ratified by one or more of the states named in SECTION 48-37-10, then such compact shall become operative and effective as between this State and such other state or states. The Governor shall take such action as may be necessary to complete the exchange of official documents as between this State and any other state ratifying such compact.