(1) A mutual association may purchase, sell, underwrite, and hold investment securities that are obligations in the form of bonds, notes, or debentures, as provided in rules adopted by the department. In addition, unless limited by the department by rule, a mutual association may purchase, sell, underwrite, and hold those investment securities that are derivative transactions that federal savings associations are expressly authorized to purchase, sell, underwrite, and hold. A mutual association may hold without limit investment securities that are general obligations of the United States, obligations that are guaranteed fully as to principal and interest by the United States, or general obligations of any state.
(2) The department may adopt rules to implement this section.