S.C. Code § 1-11-320
The department shall ensure that all state-owned motor vehicles are identified as such through the use of permanent state government license plates and either state or agency seal decals. No vehicles shall be exempt from the requirements for identification except those exempted by the department.
This section shall not apply to vehicles supplied to law enforcement officers when, in the opinion of the department after consulting with the Chief of the State Law Enforcement Division, those officers are actually involved in undercover law enforcement work to the extent that the actual investigation of criminal cases or the investigators' physical well-being would be jeopardized if they were identified. The department is authorized to exempt vehicles carrying human service agency clients in those instances in which the privacy of the client would clearly and necessarily be impaired.
S.C. Code § 1-11-320