SDCL § 25-2-21: Enforcement.

(a) A premarital agreement is not enforceable if the party against whom enforcement is sought proves that:

(1) That party did not execute the agreement voluntarily; or

(2) The agreement was unconscionable when it was executed and, before execution of the agreement, that party:

(i) Was not provided a fair and reasonable disclosure of the property or financial obligations of the other party;

(ii) Did not voluntarily and expressly waive, in writing, any right to disclosure of the property or financial obligations of the other party beyond the disclosure provided; and

(iii) Did not have, or reasonably could not have had, an adequate knowledge of the property or financial obligations of the other party.

(b) An issue of unconscionability of a premarital agreement shall be decided by the court as a matter of law.