55 ILCS 5/3-8002
The county board of every county having a county police department merit board established under the County Police Department Act (repealed) or a merit commission for sheriff's personnel established under Section 58.1 of "An Act to revise the law in relation to counties", approved March 31, 1874, as amended (repealed), shall adopt and implement the merit system provided by this Division and shall modify the merit system now in effect in that county as may be necessary to comply with this Division.
The county board of any county having a population of less than 1,000,000 which does not have a merit board or merit commission for sheriff's personnel may adopt and implement by ordinance the merit system provided by this Division. If the county board does not adopt such a merit system by an ordinance and if a petition signed by not fewer than 5% or 1000, whichever is less, of the registered electors of any such county is filed with the county clerk requesting a referendum on the adoption of a merit system for deputies in the office of the Sheriff, the county board shall, by appropriate ordinance, cause the question to be submitted to the electors of the county, at a special or general election specified in such ordinance, in accordance with the provisions of Section 28-3 of the Election Code. Notice of the election shall be given as provided in Article 12 of that Code . If a majority of those voting on the proposition at such election vote in favor thereof, the county board shall adopt and implement a merit system provided in this Division. When a merit board or merit commission for sheriff's personnel has been established in a county, it may be abolished by the same procedure in which it was established.
This Division does not apply to any county having a population of more than 1,000,000 nor to any county which has not elected to adopt the merit system provided by this Division and which is not required to do so under this Section.
55 ILCS 5/3-8002