If there is one thing we know for certain about the term "Waters of the United States" (WOTUS) under the Clean Water Act (CWA), it is that its definition remains uncertain.

The breadth of the definition ebbs and flows with each Republican or Democratic administration, and courts have struggled to apply definitions uniformly following the 2006 disjointed decision in Rapanos v. U.S., in which significantly different tests were propounded by the plurality led by Justice Scalia and by the concurring opinion of Justice Kennedy. In just the last few years, we have seen two different definitions adopted by the Obama and Trump administrations leading to circuit splits, with some enforcing and others staying the rules, that have contributed to the continued fragmentation of WOTUS.

As the Biden administration works on its own version of WOTUS, the U.S. Supreme Court granted a petition for a writ of certiorari in Sackett v. EPA, which could reshape the definition of WOTUS. In simple terms, the decision may clarify which of Justice Kennedy's "significant nexus" test or Justice Scalia's narrower "relatively permanent" definition is right.

What's at Stake?

Practically speaking, the WOTUS definition is most relevant to CWA jurisdictional determinations, which in turn may require a person engaged in activities affecting waters of the United States to obtain a permit.

The uncertainty surrounding the WOTUS definition has made it difficult for potentially regulated entities to determine which of their activities may be subject to CWA permitting requirements and has led to the same activities being regulated in some states under the significant nexus test but not in others following Justice Scalia's test. The Supreme Court could now bring some uniformity to WOTUS—or perhaps not, as explained below.

Will It Matter for Your Project?

Project developers and permit applicants may anxiously be waiting for an answer from the Supreme Court that could affect whether their activities are covered under the CWA, but not all will be affected the same way. If the Supreme Court's conservative majority decisively adopts Justice Scalia's test, those who do not yet have an approved jurisdictional determination (AJD) from the U.S. Army Corps of Engineers may indeed escape CWA jurisdiction. But what of those who already received an AJD or are currently covered by a CWA permit?

It is likely that only a small share of covered entities would be affected. First, unless the Court revolutionizes the WOTUS definition, an entity covered under a well-accepted component of the rules, such as traditional wetlands or tributaries, will still be covered. Second, even an entity covered under a more controversial component of the rules may not get immediate relief.

AJDs are valid for five years, and while the Corps may reconsider an existing AJD before it expires, such reconsideration is generally justified by drastically changed conditions on the ground rather than judicial decisions. Accordingly, an applicant with a recent AJD may be better off assuming continued jurisdiction and applying for a permit to proceed with a particular project rather than waiting for a hypothetical chance to avoid jurisdiction.

Because WOTUS is never simple, the Biden administration may publish a new rule while the Sackett case is pending and argue that the case should be dismissed for mootness. However, there is a good chance that a decision from the conservative-led Court would be at odds with any new WOTUS rule adopted by the White House. In short, while the Supreme Court could provide clarity to the definition of WOTUS, the floodgates are far from closed.