S.D. Codified Laws § 55-1-21.6
Discretion of trustee of purpose trust
Except as otherwise provided in the governing instrument, a trustee of a purpose trust is vested with full discretion in:
(1) Interpreting the purposes of the trust consistent with the terms of the governing instrument; and
(2) Applying, distributing, or expending principal and income to further the trust's purposes.
Source: SL 2018, ch 275, § 9.