The U.S. Supreme Court has issued its long-awaited ruling in Sackett v. EPA, addressing the “nagging question” of what bodies of water are included in the Clean Water Act’s definition of “waters of the United States.” The scope of the definition is important because waters of the United States are subject to regulation by the Environmental Protection Agency and the Army Corps of Engineers under the Clean Water Act.

The case focused on whether wetlands are waters of the United States. The majority opinion, authored by Justice Samuel Alito, concluded that the Clean Water Act applies only to wetlands that have “a continuous surface connection to bodies that are ‘waters of the United States’ in their own right so that they are indistinguishable” from those waters.

In other words, the EPA and the Army Corps of Engineers can only assert jurisdiction over a wetland with a continuous surface connection to a relatively permanent body of water that is, or is connected to, a traditional interstate navigable body of water such as a lake, river or ocean.

The continuous surface connection standard provides a clearer and more limited definition of waters of the United States than previous definitions, and creates a significant check on the EPA’s power over property owners. The decision also effectively strikes the agency’s 2023 Waters of the United States (WOTUS) Rule, even though the court did not directly address it in its opinion.

This is the latest in a long line of cases and regulations in the waters of the United States debate. The last Supreme Court case that addressed the issue was Rapanos v. U.S., which was released in 2006. There, the Court failed to provide a definite answer to whether wetlands are included in the waters of the United States definition. A fractured court produced three opinions with three different answers. Because none of three opinions secured the support of a majority of the justices, none became mandatory precedent.

As a result, the EPA and Army Corps of Engineers could issue regulations consistent with any of the three Rapanos opinions. The regulations challenged in Sackett followed the “significant nexus” test set forth in Justice Kennedy’s opinion in Rapanos, which provided that wetlands with a significant nexus to traditional navigable waters were subject to the Clean Water Act. Such a nexus was said to exist when the “wetlands, either alone or in combination with similarly situated lands in the region, significantly affect the chemical, physical and biological integrity” of traditional navigable waters.

Many property owners were critical of the significant nexus test because of its broad scope. It enabled the overseeing agencies to use various open-ended hydrological and ecological factors to assert jurisdiction even over isolated ditches and ponds, under the rationale that these bodies affected distant lakes, rivers or oceans. Property owners thus faced uncertainty over whether wetlands on their properties were subject to the Clean Water Act. If triggered, the law imposes restrictions on property development, expensive and time-consuming permitting processes, as well as civil and criminal penalties.