18-101.Grounds.

Quo warranto — "by what warrant" — challenges someone's authority to hold an office, exercise a franchise, or claim a privilege they may not lawfully possess. Section 18-101 lists six distinct situations where the proceeding is available in Illinois.

The first two grounds target individuals: someone who usurps, intrudes into, or unlawfully holds any office or franchise, including an office in a state-chartered corporation; and someone who holds or claims a privilege, exemption, or license that was improperly or unlawfully issued. The third covers a public officer who has done, or allowed, an act that works a forfeiture of their office under existing law.

The remaining three grounds address organizations. One reaches an association acting as a corporation in Illinois without being legally incorporated. Another reaches a corporation that surrenders or forfeits its rights and privileges, or exercises powers the law never conferred on it. The last is a specific, historically rooted ground: a railroad company charging extortionate freight or passenger rates, or unjustly discriminating in its rate structure.

Because these grounds are distinct — individual office-holding, corporate existence, corporate overreach, and railroad rate practices — the remedy each ground supports differs in focus even though all six proceed under the same quo warranto framework.