547 U.S. 715 (2006), U.S. Supreme Court
Rapanos v. United States is a landmark Clean Water Act (CWA) case that reshaped, and for years destabilized, the federal definition of "waters of the United States" (WOTUS).
What is the proper scope of "waters of the United States" under the Clean Water Act with respect to wetlands adjacent to nonnavigable tributaries of navigable waters—specifically, do wetlands lacking a continuous surface connection to navigable waters fall within federal jurisdiction when connected through man-made drains or intermittent channels?
No single majority opinion defined a single controlling rule. The Court produced two principal tests: - Plurality (Scalia, joined by Roberts, Thomas, Alito): The CWA covers only (1) relatively permanent, standing or continuously flowing bodies of water forming geographic features commonly understood as streams, oceans, rivers, and lakes; and (2) wetlands that have a continuous surface connection to such relatively permanent waters such that it is difficult to determine where the water ends and the wetland begins. Ephemeral flows and mere hydrologic connections are insufficient. - Concurrence in the judgment (Kennedy): A water or wetland is covered if it, "either alone or in combination with similarly situated lands in the region, significantly affects the chemical, physical, and biological integrity" of traditional navigable waters—i.e., there is a "significant nexus" between the wetland/tributary and navigable-in-fact waters. Mere adjacency in the Corps' categorical sense is not enough; jurisdiction requires case-specific evidence of significant effects. Because there was no majority, many lower courts applied Marks v. United States to treat Justice Kennedy's significant nexus test as the controlling standard (as the narrowest grounds) or held that jurisdiction exists if either the plurality's test or Justice Kennedy's test is satisfied.
Judgments of the Sixth Circuit were vacated and the cases remanded. The Court did not adopt a single definitive standard for CWA jurisdiction over wetlands. The plurality would require proof of a continuous surface connection to relatively permanent waters; Justice Kennedy would require proof of a significant nexus to navigable waters. On remand, the government was required to establish jurisdiction under one of these approaches.
Rapanos reoriented CWA jurisprudence by rejecting the Corps' most expansive theories and forcing courts to scrutinize the nature of connections between wetlands, tributaries, and navigable waters. It introduced enduring vocabulary—"relatively permanent" waters, "continuous surface connection," and "significant nexus"—that dominated WOTUS debates, compliance counseling, and expert hydrology in litigation. Doctrinally, Rapanos illustrates how fractured opinions can nonetheless supply operative law via Marks and how administrative deference interacts with statutory text, federalism, and scientific complexity. Practically, it drove extensive rulemaking (e.g., 2015 Clean Water Rule, 2020 Navigable Waters Protection Rule, subsequent WOTUS rules) and uneven enforcement nationwide. In 2023, Sackett v. EPA rejected the significant nexus test and adopted an approach closer to the Rapanos plurality for wetlands, underscoring Rapanos's role as the pivot point in the Court's narrowing of CWA jurisdiction.