65 ILCS 5/3.1-40-50
Every resolution and motion specified in Section 3.1-40-45, and every ordinance, that is returned to the city council by the mayor shall be reconsidered by the city council at the next regular meeting following the regular meeting at which the city council receives the mayor's written objection. If, after reconsideration, two-thirds of all the alderpersons then holding office on the city council agree at that regular meeting to pass an ordinance, resolution, or motion, notwithstanding the mayor's refusal to approve it, then it shall be effective. The vote on the question of passage over the mayor's veto shall be by yeas and nays and shall be recorded in the journal.
This Section does not apply to municipalities with more than 500,000 inhabitants.
65 ILCS 5/3.1-40-50