Section 735 ILCS 5/2-408 - Intervention(a) Upon timely application anyone shall be permitted as of right to intervene in an action: (1) when a statute confers an unconditional right to intervene; or (2) when the representation of the applicant's interest by existing parties is or may be inadequate and the applicant will or may be bound by an order or judgment in the action; or (3) when the applicant is so situated as to be adversely affected by a distribution or other disposition of property in the custody or subject to the control or disposition of the court or a court officer.(b) Upon timely application anyone may in the discretion of the court be permitted to intervene in an action: (1) when a statute confers a conditional right to intervene; or (2) when an applicant's claim or defense and the main action have a question of law or fact in common.(c) In all cases involving the validity of a constitutional provision, statute or regulation of this State and affecting the public interest, the State upon timely application may in the discretion of the court be permitted to intervene.(d) In all cases involving the validity of an ordinance or regulation of a municipality or governmental subdivision of this State and affecting the public interest, the municipality or governmental subdivision upon timely application may in the discretion of the court be permitted to intervene.(e) A person desiring to intervene shall present a petition setting forth the grounds for intervention, accompanied by the initial pleading or motion which he or she proposes to file. In cases in which the allowance of intervention is discretionary, the court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties.(f) An intervenor shall have all the rights of an original party, except that the court may in its order allowing intervention, whether discretionary or a matter of right, provide that the applicant shall be bound by orders or judgments, theretofore entered or by evidence theretofore received, that the applicant shall not raise issues which might more properly have been raised at an earlier stage of the proceeding, that the applicant shall not raise new issues or add new parties, or that in other respects the applicant shall not interfere with the control of the litigation, as justice and the avoidance of undue delay may require.