S.C. Code § 25-1-510
All commissioned and warrant officers of the South Carolina National Guard shall be appointed and commissioned or warranted by the Governor. No person must be appointed and commissioned or warranted unless he is a citizen of the United States and meets federal residency requirements for the appointment. His age shall conform to the age requirements as set forth in the regulations issued by the National Guard Bureau and that are in effect at the time of appointment. Every commissioned or warrant officer must hold office under his commission or warrant until he has been regularly appointed and commissioned or warranted to another grade or office or until he has been regularly retired, discharged, dismissed, or placed in an inactive status.
S.C. Code § 25-1-510