615 ILCS 50/1.2
The Department is designated as the agency to control and regulate the diversion of Lake Michigan water and is responsible for apportionment of water diverted from the Lake Michigan watershed. No regional organization, municipality, political subdivision, agency or instrumentality, or any other organization, association or individual within the State of Illinois desiring to divert water from Lake Michigan shall do so without first obtaining a valid allocation permit from the Department. The Department shall not allocate water diverted from Lake Michigan for use outside the boundaries of this State and any other Great Lake state without the approval of the other Great Lakes states and the International Joint Commission. The Department shall cooperate with the International Joint Commission, Federal Agencies and state and local agencies, for the regulation and maintenance of the levels and use of the waters of Lake Michigan and the other Great Lakes.
615 ILCS 50/1.2