805 ILCS 310/17

All co-operative corporations and joint stock corporations, companies, associations, voluntary unincorporated associations or partnerships heretofore organized under prior statutes, or who shall be doing business as co-operative institutions with the objects enumerated in this Act, shall have the benefit of the provisions of this Act and be bound thereby, on filing with the Secretary of State a written declaration, signed and sworn to by the president and secretary, to the effect, that it or they, have by a two-thirds vote of its shareholders or its members, decided to accept the benefits of this Act and be bound by the same.