Mich. Comp. Laws § 331.8s
A hospital authority, heretofore organized and operating pursuant to this act, shall have all the authority and rights granted under this act or any amendments thereto, relative to the construction of community hospitals, operation of same, issuance of bonds therefor, and pledging of income and revenues therefor, including the amounts assessed to the various member communities. An action of the hospital authority board of any hospital authority in the adoption of a resolution for the issuance of bonds and any proceedings taken under the resolution and law in relation thereto prior to the effective date of this amendatory act is hereby validated, ratified, and confirmed, and the hospital authority board of any such hospital authority may issue, sell, and deliver the bonds authorized by such actions and proceedings in the manner prescribed by law.
MCL 331.8s