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January/February 2024

Relatively (im)permanent: The ever-changing scope of the Clean Water Act

Shawn Hagerty, Rebecca J Andrews, and Samuel Johnson


  • Despite the U.S. Supreme Court’s intention to provide a final answer to the “nagging question of the outer reaches of the CWA,” ambiguities in the Sackett decision will result in a continued debate on the true meaning of WOTUS. 
  • Explores the Conforming Rule and examines how various agencies are adjusting their regulations to adhere to the Court's more precise definition of WOTUS.
Relatively (im)permanent: The ever-changing scope of the Clean Water Act
Pola Damonte via Getty Images

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In Sackett v. EPA, 598 U.S. 651, 143 S.Ct. 1322 (2023), the U.S. Supreme Court (the Court) addressed the most basic question about the Federal Water Pollution Control Act, commonly known as the Clean Water Act (Act)—where does it apply? More specifically, the Court assessed the meaning of “waters of the United States” (WOTUS), the words used to define the Act’s jurisdictional scope. While the Court may have intended to use Sackett to provide a final answer to what it termed the “nagging question of the outer reaches of the CWA,” ongoing and future litigation, proposed legislation, and ambiguities in the decision itself will result in a continued debate on the true meaning of WOTUS.

A 50-year question addressed

The Act is the principal federal law regulating water pollution in the United States. It prohibits “the discharge of any pollutant by any person” into “navigable waters” except as authorized by a permit. In almost a tautological fashion, the Act then defines the scope of “navigable waters,” to mean “the waters of the United States, including the territorial seas.” 33 U.S.C. § 1362(7).  Because this brief definition provides little guidance, the Environmental Protection Agency (EPA) and the Army Corps of Engineers (Corps) (agencies) have provided more detailed definitions over time. By 1975, the WOTUS definition extended to traditional navigable waters, tributaries and included “adjacent wetlands.” Since then, the Corps has interpreted “adjacent” to mean more than “adjoining” and includes waters separated by man-made dikes or barriers, natural river berms, beach dunes, and the like.

In 1977, Congress seemingly ratified the regulatory definition when it amended the Act to allow states to assume permitting duties for discharges of dredged or fill material to WOTUS, except for traditional navigable waters, including wetlands adjacent thereto. 33 U.S.C. § 1344(g)(1). By using the phrase “wetlands adjacent thereto” as an exemption to (and thus a subset of) the broader term WOTUS, Congress further cemented federal protection for wetlands. But the question remained: to what extent?

Uncertainty around this “nagging question” led to several attempts by the agencies and the Court to clarify where WOTUS begins and ends. This history can be mind-numbing for all but the most ardent water quality aficionados. The key points are that 1. the agencies’ WOTUS regulations have expanded and contracted its definition over the years; 2. on three occasions before Sackett, the Court assessed those regulations or agency actions in an attempt to fix the Act's jurisdiction; and 3. the current Court appears to believe that the agencies had ignored its previous guidance. This left a messy and confusing framework for WOTUS determinations, which included the “significant nexus test,” a fact-specific analysis.

The majority in Sackett tried to draw a “clear demarcation” between WOTUS and non-WOTUS. Specifically, the Court majority now adopted the prior plurality formulation in Rapanos v. United States, 547 U.S. 715 (2006) and concluded that WOTUS are “only those relatively permanent, standing or continuously flowing bodies of water' forming geographic[al] features' that are described in ordinary parlance as 'stream, oceans, rivers and lakes.’” Sackett, supra, 598 U.S. at 678–79. The Act, therefore, only extends to 1. traditional interstate navigable waters; 2. relatively permanent bodies of water connected to traditional interstate navigable waters; and 3. wetlands that have a continuous surface connection with waters in points one or two above, thus making it difficult to determine where the “water” ends and the “wetlands” begins. While the Court majority describe this standard as based on a clear interpretation of the statutory language, the opinion of Justices Kavanaugh, Kagan, Sotomayor, and Jackson, concurring only in the judgment highlights an intense debate over the meaning of those words even within the Court. Sackett, supra, 598 U.S. at 715–28 (concurring opinion).

Regulatory responses

Immediately following Sackett, the agencies began aligning their regulations to the Court's narrower definition of WOTUS. On September 8, 2023, the agencies finalized the Revised Definition of “Waters of the United States” Conforming (Conforming Rule), which removed the significant nexus test once and for all. First articulated in Justice Kennedy's concurring opinion in Rapanos v. United States, 547 U.S. 715 (2006), the significant nexus test sought to reconcile legal line drawing and hydrological complexity by extending federal jurisdiction to waters that “alone or in combination with similarly situated waters in the region, significantly affect the chemical, physical, or biological integrity” of traditional navigable waters. See 88 Fed. Reg. 3301, “Revised Definition of Waters of the United States” (Jan. 18, 2023). The Sackett Court expressly rejected this approach, finding the Act “does not define the EPA's jurisdiction based on ecological importance . . . .” For the Sackett Court, the test defied the Act's legislative intent and unduly burdened property owners with uncertainty regarding their rights.

Keeping with Sackett's language, the Conforming Rule extends protections to only those wetlands that have a “continuous surface connection” to traditional navigable waters or their “[r]elatively permanent, standing or continuously flowing” tributaries and impoundments. See 88 Fed. Reg. 61, 964 (Sept. 8, 2023) [changes to 33 C.F.R. § 328.3 [adopting changes to Army Corps regulations]; 40 C.F.R. § 120.2 [adopting changes to EPA regulations]. Similarly, the agencies removed language that brought all “interstate wetlands” under their jurisdiction. The blanket protection for wetlands directly contradicted the Court's conclusion that interstate waters should be understood to mean traditional “open waters.” To be sure, interstate wetlands remain within the Act's purview to the extent they meet the continuous surface connection standard. Equally certain is that the latest joint rule issued by EPA and the Army Corps is also likely to be challenged, particularly given that there was no “notice and comment” period prior to adoption of the final rule.

A split in WOTUS regimes

To complicate matters, the Conforming Rule is only operative in 23 states and the District of Columbia. Meanwhile, the agencies apply 1986/1988 regulations (but consistent with the Sackett decision) in the remaining 27 states. The regime split results from three separate preliminary injunctions imposed on the January 2023 Rule. See Texas v. EPA, No. 3:23-CV-17, (S.D. Tex. Mar. 19, 2023); West Virginia v. EPA, No. 3:23-CV-032, (D.N.D. Apr. 12, 2023); Commonwealth of Kentucky v. EPA, Nos. 23–5343/5345, Doc. No. 24 (6th Cir. May 10, 2023). In June, EPA appealed the injunction in West Virginia only to drop it after issuing the Conforming Rule. The injunctions create a patchwork regulatory scheme across the states that will remain as plaintiffs and defendants refocus their arguments in respective courts. This November, Plaintiffs filed amended complaints to challenge the Conforming Rule. The Congressional Research Service depicted the current split in an updated June 2023 report figure:

Figure 1. Status of 2023 WOTUS Rule as of June 22, 2023

Figure 1. Status of 2023 WOTUS Rule as of June 22, 2023

Source: CRS.

Legislative response to Sackett

The battle over WOTUS is not exclusive to the courts. On October 17, Democratic House members introduced H.R. 5983 (Bill). The Bill would undo Sackett and give the Act its broadest scope to date. The Bill would expand protections to 1. all waters subject to the ebb and flow of the tide, 2. the territorial seas, and 3. all interstate and intrastate waters, including intermittent and ephemeral streams and wetlands. Under the proposed law, the only constraint remaining on the Act's jurisdiction would be constitutional limits on legislative power. The Bill will face considerable opposition and will undoubtedly fail in the current Congress. Still, it will unlikely to be the last time WOTUS legislation winds through congressional halls and, perhaps, onto the president’s desk.


The majority in Sackett sought to define the outer reaches of the Act simply and concretely. While the decision answers one “nagging question” and thus ends 50 years of debate, it also opens a new chapter in the ongoing implementation of the Act. One thing is clear—the only relatively permanent result of the decision is continuous questions and more litigation.

*For a review of the new “Conforming Rule” and possible future challenges to that rule, see Susan L. Stephens, “Here We Go Again: EPA Releases Amendments to WOTUS Rule Post-Sackett Trends (Nov./Dec. 2023).