SDCL § 15-9-23: Action by assignee subject to setoff or defense--Negotiable instruments excepted.

In case of an assignment of a thing in action, the action by the assignee shall be without prejudice to any setoff or other defense existing at the time of, or before notice of the assignment; but this section shall not apply to a negotiable promissory note or bill of exchange, transferred in good faith and upon good consideration before due.