SDCL § 47-1A-732.1: Form, approval, amendment, and term of shareholder agreements.

Any agreement authorized by § 47-1A-732 shall be:

(1) Set forth in the articles of incorporation or bylaws and approved by all persons who are shareholders at the time of the agreement, or in a written agreement that is signed by all persons who are shareholders at the time of the agreement and is made known to the corporation;

(2) Subject to amendment only by all persons who are shareholders at the time of the amendment, unless the agreement provides otherwise; and

(3) Valid for ten years, unless the agreement provides otherwise.