The Great Lakes Compact became U.S. federal law in 2008.
The agreement is formally the Great Lakes–St. Lawrence River Basin Water Resources Compact. It was signed by the eight Great Lakes states in 2008 and received congressional consent and presidential approval that year. The compact establishes principles for managing withdrawals and diversions from the basin.
The eight states are Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin. The agreement also works alongside a parallel arrangement involving Ontario and Quebec.
The compact does not prohibit every use of Great Lakes water. Instead, it sets standards and review procedures, with special restrictions on diversions outside the basin. A common mix-up is the Great Lakes Charter of 1985, an earlier nonbinding regional agreement that preceded the compact.