The US Environmental Protection Agency (EPA) and Army Corps of Engineers Friday released a finalized definition of “waters of the United States” (WOTUS) in the context of the country’s Clean Water Act (CWA). The CWA was first enacted in 1972, and multiple administrations have since attempted to revise what protectable waters entail and who defines them.

Under the Obama administration in 2015, the EPA revised the CWA (2015) to include tributaries and wetlands by using a “significant-nexus” analysis, which determines whether a tributary or wetland can affect the quality of a navigable body of water. This new rule was contested on the basis of administrative overreach, but the revision was ultimately accepted after a 2018 Supreme Court ruling. Following complaints by fossil fuel executives, real estate developers and farmers, the Trump administration revised the definition in the CWA (2020) to reduce the capability of the EPA to regulate waterways. The administration questioned the EPA’s authority to perform significant-nexus analyses when determining which waterways are subject to their regulation.

This revision to the CWA may affect the outcome of a case currently before the US Supreme Court. Petitioners Michael and Chantell Sackett are challenging a compliance order they received from the EPA after the purchase of a small parcel of land in Idaho that interfered with what at the time was classified as protectable waters. The Supreme Court heard the first oral arguments for this review in October. This is the second case concerning the Sacketts’ challenge to be heard by the court.

In the Sacketts’ previous 2012 Supreme Court case, the court unanimously ruled that compliance orders under the act are final agency actions by the EPA but also that they can be contested in judicial review, remanding the case to lower courts for further proceedings.

In 2020, when the Trump administration changed the definition of controllable waters, the compliance order to the Sacketts was rescinded, and the EPA filed a motion to dismiss their continued litigation of the case. This motion was denied and the case was again argued at the Ninth Circuit, where the court continued to affirm previous holdings that the agency’s action was appropriate. The Sacketts then filed a petition for the Supreme Court to officially decide the appropriate test for wetland jurisdiction.