65 ILCS 20/21-16

Veto by mayor.

Upon the veto of any ordinance by the mayor, if two-thirds of all the members elected to the city council fail to pass the same, the veto of the mayor to the contrary notwithstanding, said ordinance shall not again be considered, unless or until introduced as an original ordinance, at a subsequent meeting. But this Section shall not be construed to prevent the introduction and consideration of a substitute or amended ordinance.