SDCL § 53-4-10: Mistake of law defined.

A mistake of law in relation to consent to contract constitutes a mistake resulting in voidable consent only when it arises from:

(1) A misapprehension of the law by all parties, all supposing that they knew and understood it and all making substantially the same mistake as to the law; or

(2) A misapprehension of the law by one party of which the others are aware at the time of contracting, but which they do not rectify.