Michigan Compiled Laws, Chapter 120. Port Districts § 120.122

Sec. 22. (1) An authority created under this act shall be exempt from and shall not be required to pay taxes on property, both real and personal, belonging to the authority, which is used exclusively for a public purpose. However, the exemption shall not apply to property belonging to an authority while a private enterprise is a lessee of the property under a written lease. The bonds, notes, or other evidences of indebtedness, or their transfer, issued by an authority as authorized in this act, the interest thereon, the income derived, and the profit from a sale, shall be exempt from taxation, other than inheritance and estate taxes, within this state.

(2) This section constitutes a covenant and agreement with the holders of bonds, notes, or other evidences of indebtedness issued by an authority.