30 ILCS 520/2

The board of trustees or other officer or officers in charge of every institution in the State of Illinois, which is supported in whole or in part by public funds, who are authorized or required to purchase commodities for use in the operation of any such institution, shall, in purchasing such commodities from vendors in any other state, give preference to vendors in those states whose preference laws do not prohibit the purchase by the public institutions of such states of commodities grown or produced in Illinois.