S.C. Code § 58-17-1900
All contracts and agreements between railroad companies doing business in this State as to rates of freight and passenger tariffs must be submitted to the Office of Regulatory Staff for inspection and correction, that it may be seen whether or not they are in violation of the law, of the provisions of the Constitution or of the rules and regulations of the commission, and all arrangements and agreements whatever as to the division of earnings of any kind by competing railroad companies doing business in this State shall be submitted to the Office of Regulatory Staff for inspection and approval, insofar as they affect rules and regulations made by the commission to secure to all persons doing business with such companies just and reasonable rates of freight and passenger tariffs and so far as they are affected by any of the provisions contained in this chapter for securing to all persons just, equal, and reasonable facilities for the transportation of freight and passengers. The commission may make such rules and regulations as to such contracts and agreements as may be considered necessary and proper. Any agreements not approved by the commission or by virtue of which rates shall be charged exceeding the rates fixed for freight and passengers shall be violations of this chapter and are unlawful and void.
S.C. Code § 58-17-1900