A recent decision by the U.S. District Court for the District of Arizona vacated and remanded the 2020 Navigable Waters Protection Rule (NWPR) issued by the Environmental Protection Agency (EPA) and U.S. Army Corps of Engineers (Corps) (together, “Agencies”) that clarified the scope of federal jurisdictional “Waters of the United States” (WOTUS) under the Clean Water Act (CWA). Before the promulgation of the NWPR, there had been several rulemakings and much litigation on this complicated issue, causing nationwide confusion on the application of a uniform standard. In 2015, the Obama administration promulgated a WOTUS rule that had been the subject of significant litigation, which the Trump administration had repealed (the “Repeal Rule”). The NWPR sought to provide certainty as to which waterbodies meet the features of WOTUS by creating clear categories of jurisdictional waterbodies.

In Pasqua Yaqui Tribe v. EPA, Case No. 4:20-cv-00266, in response to a challenge to the NWPR, the Agencies requested that the court voluntarily remand the rule for reconsideration of the definition of WOTUS. In addition to remanding the rule consistent with the Agencies’ request, the court found that the WOTUS definition had “fundamental, substantive flaws” regarding its scientific foundation and even conflicted with government reports. According to the court, such an error could not “be cured without revising or replacing the NWPR’s definition.”

It is not clear if the district court’s ruling is intended to apply nationwide, which re-introduces the considerable uncertainty that had faced the regulated community before the NWPR was finalized as to which prior interpretation of WOTUS applies. The court has requested additional briefing on the Repeal Rule, and a ruling on this issue could provide some clarity on how to interpret WOTUS. Before the court’s decision in Pasqua Yaqui Tribe, the Agencies had already announced their intention to revise the NWPR’s definition of WOTUS and revert to a pre-2015 version of the rule.