S.C. Code Ann. § 11-35-4820: Selective mandatory opting.

As prescribed in regulation by the board, any local public procurement unit may purchase from or through the State at any time; provided, however, that the board may impose a requirement upon the localities for mandatory opting in or out of any particular contract before it is established. Mandatory opting shall be imposed only where it is necessary to obtain more cost effective contracts for the State.