On January 18, 2017, the United States Court of Appeals for the Second Circuit issued a decision in Catskill Mountains Chapter of Trout Unlimited, Inc. v. EPA, which reinstated the US Environmental Protection Agency’s (EPA’s) Water Transfers Rule. The Rule, adopted in 2008, codifies EPA’s longstanding policy that water transfers between navigable waters that do not subject the water to an intervening industrial, municipal, or commercial use do not constitute an “addition of pollutants” to navigable waters and are not subject to National Pollutant Discharge Elimination System permits under section 402 of the federal Clean Water Act (CWA). The Second Circuit reversed a US District Court for the Southern District of New York decision that had vacated the Water Transfers Rule. The Second Circuit found that the Rule, which is based on the “unitary waters” reading of the statutory language, was a reasonable interpretation of the CWA and should be afforded deference under the US Supreme Court’s two-part test for judicial review of an agency’s formal interpretation of a statute in Chevron U.S.A., Inc. v. Natural Resources Defense Council Inc., 467 U.S. 837 (1984).