(40 ILCS 5/21-105) (from Ch. 108 1/2, par. 21-105)
    Sec. 21-105. Retirement systems - election of coverage. A referendum on the question of coverage under the Social Security Act may be authorized by the Governor with respect to any retirement system, or by the board of trustees of such system, or by the governing body of any political subdivision which has established a retirement system, except for a retirement system established under Article 3, 4, 5 or 6 of this Code.
    Such a referendum shall also be held upon petition signed by at least 10% of the members of any retirement system except for a retirement system established under Article 3, 4, 5 or 6 of this Code. Such petition shall be examined and checked by the governing body or board of trustees of the retirement system, and such board or body shall certify that each signer of the petition is an eligible member qualified to vote in such referendum, and that the names of all ineligible individuals have been stricken.
    Prior to a referendum on that question and to the notice of the referendum required by either Section 218(d)(3) or 218(d)(7) of the Social Security Act, a plan of coverage shall be formulated by the governing body of each retirement system or Board of Trustees, as the case may be, whose members are to participate in the referendum for the coordination of the retirement system with the social security insurance provisions of Title II of the Social Security Act.
    Where a retirement system is governed by an Act of the State of Illinois, such plan of coverage shall be presented to the General Assembly for enactment by amendment to such Act.
    The ballot to be used in the referendum shall contain a clear description of the plan of coverage, which description may take the form of a summary statement setting forth the changes or revisions, if any, to be made in the benefit and contribution provisions of the retirement system, and the obligations to be imposed upon the members of the system if the plan of coverage is approved in the referendum and their positions are included under an agreement pursuant to the provisions of this Article.
    The referendum shall be subject to the following conditions:
    (a) Only eligible employees as defined in Section 218(d)(3) of the Social Security Act shall be permitted to vote.
    (b) Should such referendum under Section 218(d)(3) fail to obtain approval, any subsequent referendum among members of the retirement system in question shall not be held for a period of at least 3 years from the date of the referendum.
    (c) Upon receipt of satisfactory proof that the conditions of the referendum specified in either Section 218(d)(3) or Section 218(d)(7) of the Social Security Act have been met, the Governor or an official of the State designated by him shall so certify to the Secretary. Proper steps to give effect to the results of the referendum shall then be taken by the State Agency, and a modification to the Federal-State Agreement shall be executed in accordance with Section 21-108 within a period of 2 years from the date of the referendum.
(Source: P.A. 84-1028.)