(a) Whenever an authority has been incorporated by 2 or more municipalities, any 1 or more of such municipalities may withdraw therefrom and any municipality not having joined in the original incorporation may join in the authority, but no municipality shall be permitted to withdraw from any authority after an obligation has been incurred by the authority.
(b) Any municipality wishing to withdraw from or to become a member of an existing authority shall signify its desire by resolution or ordinance after an enabling referendum. If the authority shall by resolution express its consent to such withdrawal or joining, articles of withdrawal or articles of joinder, as the case may be, shall be executed by the proper officers of the withdrawing or incoming municipality and shall be joined by the proper officers of the governing body of the authority and, in the case of a municipality seeking to become a member of the authority, also by the proper officers of each of the municipalities that are then members of the authority, pursuant to resolutions or ordinances by the governing bodies of such municipalities. In the case of a certificate of joinder, the certificate shall set forth all of the information required in the case of original incorporation insofar as it applies to the incoming municipality including the name and address and term of office of the first member of the board of the authority from the incoming municipality. Articles of withdrawal and articles of joinder shall be filed with the Secretary of State, who shall receive the same and endorse thereon the date and time of such receipt. If the Secretary of State finds that the articles of withdrawal or articles of joinder, as the case may be, conform to law, the Secretary of State shall forthwith endorse the Secretary of State's own approval thereon and issue a certificate of approval to which shall be attached a copy of the approved articles. Upon the issuance of such certificate of approval by the Secretary of State, said articles of withdrawal or articles of joinder, as the case may be, shall become effective and be in full force and effect, and such articles shall be conclusively deemed to have been lawfully and properly adopted. Promptly after the issuance of a certificate of approval the Secretary of State shall record the articles of withdrawal or articles of joinder, as the case may be, together with the endorsements thereon, in the book kept by it for the purpose of recording articles of incorporation.