70 ILCS 1505/25.6
The provisions of Sections 25.1 to 25.9, both inclusive, of this Act as now enacted and as may hereafter be amended, and of any ordinance or other proceeding authorizing the issuance of bonds under the provisions of Sections 25.1 to 25.9, both inclusive, of this Act as now enacted and as may hereafter be amended, shall constitute a contract with the holders of such bonds, and any holder of a bond or bonds, or any of the coupons of any bond or bonds of the Chicago Park District, issued under Sections 25.1 to 25.9, both inclusive, of this Act as now enacted and as may hereafter be amended, may, by action, mandamus, injunction or other proceeding, enforce and compel the performance of all duties required by Sections 25.1 to 25.9, both inclusive, of this Act as now enacted and as may hereafter be amended, including the making and collecting of sufficient charges and fees for service and use thereof, and the application of income and revenue thereof. In the event a trust agreement or agreements are executed and delivered to secure the payment of any such bonds, the trust agreement or agreements may prescribe by whom and on whose behalf such action may be instituted to compel performance and compliance therewith and of the duties and obligations required by Sections 25.1 to 25.9, both inclusive, of this Act as now enacted and as may hereafter be amended.
70 ILCS 1505/25.6