For any municipality, special fire control district, chapter plan, local law municipality, local law special fire control district, or local law plan under this chapter:
(1) No plan shall discriminate in its benefit formula based on color, national origin, sex, or marital status.
(2)(a) If a plan offers a joint annuitant option and the member selects such option, or if a plan specifies that the member’s spouse is to receive the benefits that continue to be payable upon the death of the member, then, in both of these cases, after retirement benefits have commenced, a retired member may change his or her designation of joint annuitant or beneficiary only twice.
(b) Any retired member who desires to change his or her joint annuitant or beneficiary shall file with the board of trustees of his or her plan a notarized notice of such change either by registered letter or on such form as is provided by the administrator of the plan. Upon receipt of a completed change of joint annuitant form or such other notice, the board of trustees shall adjust the member’s monthly benefit by the application of actuarial tables and calculations developed to ensure that the benefit paid is the actuarial equivalent of the present value of the member’s current benefit. Nothing herein shall preclude a plan from actuarially adjusting benefits or offering options based upon sex, age, early retirement, or disability.
(3) Eligibility for coverage under the plan must be based upon length of service or attained age, or both, and benefits must be determined by a nondiscriminatory formula based upon:
(a) Length of service and compensation; or
(b) Length of service.