This Article has a practical goal: to convince state lawmakers of the need to regulate in a comprehensive and evenhanded manner, avoiding short-sighted fixes or politically appealing shortcuts. To accomplish that goal, Part I focuses upon another region of the country-the Colorado River Basin-where residents have also undertaken the task of managing a water system that includes two nations(The United States and Mexico) and numerous states. Learning from the successes and failures of the resultant Law of the River, this Article derives guiding principles for the emerging Law of the Lakes. Part II makes a crucial distinction between protectionism and true sustainability, examining the existing Lakes documents for evidence of each. Part III offers a description of six essential components of any sustainable water code and provides references to a menu of draftlegislative provisions available for adoption(with or without modification) by the Great Lakes states. This Article concludes with the hope that the Great Lakes states and provinces realize the tremendous opportunity now facing them and take full advantage by developing a sustainable body of water law.