Under no circumstances, except by express written agreement of the Authority and the State or a political subdivision or subdivision adopted pursuant to Article VII, Section 10, of the Constitution, shall any bonds issued by the Authority be or become an indebtedness or obligation of the State of Illinois or of any other political subdivision of or municipality within the State, nor shall any such bond or obligation be or become an indebtedness of the Authority within the purview of any constitutional limitation or provision, and it shall be plainly stated on the face of each bond that it does not constitute such an indebtedness or obligation but is payable solely from the revenues or income as aforesaid.
70 ILCS 200/200-20