S.C. Code Ann. § 16-13-332

A library or agent or employee of the library causing the arrest of any person pursuant to the provisions of Section 16-13-331 shall not be held civilly liable for unlawful detention, slander, malicious prosecution, false imprisonment, false arrest, or assault and battery of the person so arrested, unless excessive or unreasonable force is used; whether such arrest takes place on the premises by such agent or employee; provided that, in causing the arrest of such person, the library or agent or employee of the library had at the time of such arrest probable cause to believe that the person committed willful concealment of books or other library property.