See Full Constitution
Article 2

Section 14. Approval of bills; vetoes

(a) Within ten days after passage, every bill shall be signed by the presiding officers and presented to the governor. If the governor approves a bill, he shall sign it. If the governor does not approve a bill, the governor shall veto it by returning the bill, with a veto message of the objections, to the house of origin of the bill. Whenever a veto message is so received, the message shall be entered in the journal and in not more than thirty calendar days (excluding the day received), the house of origin shall reconsider the bill. If two-thirds of the members then elected (or appointed) and qualified shall vote to pass the bill, it shall be sent, with the veto message, to the other house, which shall in not more than thirty calendar days (excluding the day received) also reconsider the bill, and if approved by two-thirds of the members then elected (or appointed) and qualified, it shall become a law, notwithstanding the governor's veto.
If any bill shall not be returned within ten calendar days (excluding the day presented) after it shall have been presented to the governor, it shall become a law in like manner as if it had been signed by the governor.
(b) If any bill presented to the governor contains several items of appropriation of money, one or more of such items may be disapproved by the governor while the other portion of the bill is approved by the governor. In case the governor does so disapprove, a veto message of the governor stating the item or items disapproved, and the reasons therefor, shall be appended to the bill at the time it is signed, and the bill shall be returned with the veto message to the house of origin of the bill. Whenever a veto message is so received, the message shall be entered in the journal and, in not more than thirty calendar days, the house of origin shall reconsider the items of the bill which have been disapproved. If two-thirds of the members then elected (or appointed) and qualified shall vote to approve any item disapproved by the governor, the bill, with the veto message, shall be sent to the other house, which shall in not more than thirty calendar days also reconsider each such item so approved by the house of origin, and if approved by two-thirds of all the members then elected (or appointed) and qualified, any such item shall take effect and become a part of the bill.