S.D. Codified Laws § 5-2-15
All mortgages and sheriffs' certificates of sale in the name of the State of South Dakota shall be assignable to any person holding an inferior lien or having any other bona fide interest in the land covered by such mortgage or certificate whenever it shall appear to be to the best interest of the state to make such assignment and upon full payment of the principal and interest payable under such mortgages or certificates and the authority and power is hereby given to any board or commission having charge of any such liens to execute such assignments by and with the approval of the Governor endorsed thereon.
No such mortgage shall be assigned unless the conditions thereof have been broken. No school fund mortgage shall be assigned without approval of the board of county commissioners of the county wherein the real estate affected by such mortgage is situated.
SDCL 5-2-15