Ill. Const. art. VII, § 10

(a) Units of local government and school districts may contract or otherwise associate among themselves, with the State, with other states and their units of local government and school districts, and with the United States to obtain or share services and to exercise, combine, or transfer any power or function, in any manner not prohibited by law or by ordinance. Units of local government and school districts may contract and otherwise associate with individuals, associations, and corporations in any manner not prohibited by law or by ordinance. Participating units of government may use their credit, revenues, and other resources to pay costs and to service debt related to intergovernmental activities. (b) Officers and employees of units of local government and school districts may participate in intergovernmental activities authorized by their units of government without relinquishing their offices or positions. (c) The State shall encourage intergovernmental cooperation and use its technical and financial resources to assist intergovernmental activities. (Source: Illinois Constitution.)