South Dakota Codified Laws
Chapter 02 - Rights And Obligations Of Marriage
Section 25-2-20 - Amendment--Revocation.

25-2-20. Amendment--Revocation.
After marriage, a premarital agreement may be amended or revoked only by a written agreement signed by the parties. The amended agreement or the revocation is enforceable without consideration.

Source: SL 1989, ch 216, ยง5.