65 ILCS 5/11-1-2.1
In addition to the powers of the police of any municipality under Section 7-4-8 of this Act, the corporate authorities of each municipality having a population of less than 500,000 may enter into agreements with any other such municipality or municipalities to furnish police assistance on request. Such agreements shall contain provisions in relation to any liability, including any liability or obligation to indemnify created by Section 1-4-5 or Section 1-4-6, which may occur as a result of any police assistance furnished under such agreements.
Police officers furnishing assistance under such agreements have all of the powers of police officers of any requesting municipality and are subject to the direction of the chief of police of a requesting municipality.
65 ILCS 5/11-1-2.1