R.I. Gen. Laws § 30-3-13

All commissioned officers of the staff corps and departments, hereafter appointed, shall have had previous military experience, except chaplains, officers of the judge advocate general’s corps, and medical corps officers. They shall hold their positions until they shall have reached the age of sixty (60) years, unless retired prior to that time by reason of resignation or disability, or for cause to be determined by an efficiency board or a court-martial legally convened for that purpose. Vacancies among these officers shall be filled by appointment from the commissioned officers of the national guard or from such other civilians as may be specifically qualified for duty therein.