On August 30, 2021, the United States District Court for the District of Arizona issued an order vacating the Navigable Waters Protection Rule and remanding the rule back to U.S. EPA and the U.S. Army Corps of Engineers. The Navigable Waters Protection Rule is the Trump administration’s regulation that defines “waters of the United States,” thereby establishing the reach of the Clean Water Act regulatory and permitting scheme. The Biden administration previously announced that it intends to repeal and replace the Navigable Waters Protection Rule, but left the rule in place while it considers its next steps. 

In its decision, the court noted that the Navigable Waters Protection Rule was promulgated despite feedback from the U.S. EPA Science Advisory Board that the rule “conflicts with established science, disregards key aspects of the 2015 Connectivity Report, and weakens protection of the nation’s waters in contravention of the [Clean Water Act’s] objectives.” The court found that the seriousness of the federal agencies’ errors in enacting the rule, the likelihood that the agencies will alter the definition of “waters of the United States” set forth in the rule, and the possibility of serious environmental harm if the rule remains in place upon remand all weighed in favor of vacating and remanding the rule back to the agencies. 

In the wake of the District of Arizona decision, the earlier 1986 waters of the United States rulemaking, as interpreted by the U.S. Supreme Court in its 2006 Rapanos v. United States decision (the “significant nexus” test), is the rule in effect, at least for now. Future litigation is likely to complicate the question of whether the District of Arizona decision applies nationwide (as previously seen with the Obama-era waters of the United States rulemaking in 2015, when the country was split in terms of which iteration of the rule was in effect as a result of court challenges to the Obama-era rule).

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