55 ILCS 5/6-2010

Incontestability; payable only out of taxes levied. Notes issued under the provisions of this Division shall be incontestable after authentication by the County Treasurer and delivery to a purchaser for a valuable consideration, and in like manner and to like extent as though same were negotiable instruments, and shall be payable only out of and from the proceeds of taxes levied and described in the proceedings authorizing the issuance of the notes, and shall so state on their face, and shall not be deemed to be an obligation of the County within any constitutional or statutory limitation.