SDCL § 21-12-1: Grounds for rescission.

The rescission of a written contract may be adjudged on the application of a party aggrieved:

(1) In any of the cases mentioned in § 53-11-2;

(2) Where the contract is unlawful, for causes not apparent upon its face, and the parties were not equally in fault;

(3) When the public interest will be prejudiced by permitting it to stand.