70 ILCS 2205/10
All ordinances, orders, rules, resolutions and regulations shall before taking effect, be passed upon by the president of the board of trustees. Such as he shall approve, he shall sign, and such as he shall not approve, he shall return to the board of trustees, with his objections thereto in writing, at its next regular meeting after the passage thereof. The president's veto may extend to any one or more items or appropriations contained in any ordinance, or to the entire ordinance; and in case the veto only extends to a part of such ordinance, the remainder shall take effect and be in force; with his objections thereto by the time aforesaid, he shall be deemed to have approved the same, but in case the president shall fail to return any ordinance, order, rule, resolution or regulation and such ordinance shall take effect accordingly. Upon the return of any unapproved ordinance, order, rule, resolution or regulation, the vote by which the same was passed shall be reconsidered by the board of trustees, and if upon such reconsideration, two-thirds of all the members elect shall agree by yeas and nays to pass the same, it shall go into effect, notwithstanding the president's refusal to approve thereof.
70 ILCS 2205/10