A South Dakota special spousal trust executed during marriage is not enforceable if the spouse against whom enforcement is sought proves that:
(1) The trust was unconscionable when made;
(2) The spouse against whom enforcement is sought did not execute the South Dakota special spousal trust agreement voluntarily; or
(3) Before execution of the South Dakota special spousal trust agreement, the spouse against whom enforcement is sought:
(a) Was not given a fair and reasonable disclosure of the property and financial obligations of the other spouse;
(b) Did not voluntarily sign a written waiver expressly waiving right to disclosure of the property and financial obligations of the other spouse beyond the disclosure provided; and
(c) Did not have notice of the property or financial obligations of the other spouse.
Whether a South Dakota special spousal trust is unconscionable is determined by a court as a matter of law.