65 ILCS 5/6-4-3: Reconsideration - passage over veto.

Every ordinance, which is returned to the council by the mayor shall be reconsidered by the council. If, after such reconsideration, three-fifths of all the alderpersons then holding office on the city council agree to pass an ordinance, resolution, or motion, notwithstanding the mayor's refusal to approve it, then it shall be effective.