SDCL § 47-14A-8: Usury not a defense against beneficial owner's obligation.

No obligation of a beneficial owner or trustee of a business trust to the business trust arising under the governing instrument or a separate agreement in writing, and no note, instrument or other writing evidencing any such obligation of a beneficial owner or trustee, is subject to the defense of usury, and no beneficial owner or trustee may interpose the defense of usury with respect to any such obligation in any action.