20 ILCS 3110/5.1

Nothing contained in this Act shall be construed as limiting or restricting the power of a lessee, under paragraph (b) of Section 5, to dedicate as a nature preserve, as provided in the "Illinois Natural Areas Preservation Act", as now or hereafter amended, its interest in the land leased by such lessee from the Illinois Building Authority. However, any such dedication shall always be, and the instrument of dedication shall provide that it is, subject and subordinate to the prior rights of the Illinois Building Authority under any lease in which it is lessor and all extensions of such lease, and no such dedication shall operate to diminish or otherwise modify the obligations of the lessee under any such lease, or any extension thereof, and shall be of no effect if the lessee defaults in the performance of any of its obligations under the terms of such lease.