S.D. Codified Laws § 58-18-4
Group health insurance may be under a policy issued to the trustees of a fund established by two or more employers in the same or related industry or by one or more labor unions or by one or more employers and one or more labor unions or by an association as defined in § 58-18-3, which trustees shall be deemed the policyholder, to insure employees of the employers or members of the unions or of such association, or employees of members of such association, for the benefit of persons other than the employers or the unions or such association. The term "employees" as used herein may include the officers, managers and employees of the employer, and the individual proprietor or partners if the employer is an individual proprietor or partnership. The term "employees" as used herein may include retired employees. The policy may provide that the term "employees" shall include the trustees or their employees, or both, if their duties are principally connected with such trusteeship.
SDCL 58-18-4