In January 2017, the Second Circuit upheld the U.S. Environmental Protection Agency’s (EPA) Water Transfers Rule (Rule), reversing a decision by the Southern District of New York to vacate the Rule and remand the matter to the EPA.1 The decision in Catskill IV was greeted as a victory by many western states and water management districts, but was a disappointment for environmental organizations and downstream states that had intervened as plaintiffs. As the second federal circuit affirming the validity of the Rule, the Catskill IV court further cemented the EPA’s decision to formalize the practice of exempting water transfers from the Clean Water Act’s (CWA) permitting system.2 Although the Second Circuit cited numerous alternative mechanisms for resolving pollution disputes outside of the CWA permitting system, these mechanisms are infrequently used, unpredictable, and in some cases unavailable to the states. As a result, the holding in Catskill IV leaves the regulation of water transfers almost exclusively in the hands of individual states where water transfers occur and leaves downstream states without effective mechanisms for protecting their waterways from unwanted pollution.