Illinois constitution
Article VI
Section 5

The number of Appellate Judges to be selected from each
Judicial District shall be provided by law. The Supreme Court
shall prescribe by rule the number of Appellate divisions in
each Judicial District. Each Appellate division shall have at
least three Judges. Assignments to divisions shall be made by
the Supreme Court. A majority of a division constitutes a
quorum and the concurrence of a majority of the division is
necessary for a decision. There shall be at least one
division in each Judicial District and each division shall
sit at times and places prescribed by rules of the Supreme
Court.