225 ILCS 720/6.04
A bond with separate surety filed in accordance with this Article shall not be cancelled by the surety except after not less than 90 days notice to the Department. A surety shall not at any time cancel any portion of a bond covering land already affected. If the license to do business in Illinois of any surety on a bond filed with the Department pursuant to this Act shall be suspended or revoked, the operator, within 30 days after receiving notice thereof from the Department, shall substitute for such surety a good and sufficient corporate surety licensed to do business in Illinois. On failure of the operator to make substitution of surety as herein provided, the Department may suspend the permit of the operator until such substitution has been made.
225 ILCS 720/6.04