On February 14, 2019, the U.S. Environmental Protection Agency (EPA) and the Department of the Army (Army) published for public comment a proposed rule revising the definition of “waters of the United States,” which would establish the scope of federal regulatory authority under the Clean Water Act (CWA). The proposed rule is intended to satisfy the requirements of Executive Order (EO) 13778 that directed the EPA and the Army to review and rescind or replace the 2015 Clean Water Rule (80 FR 37053) and consider interpreting the scope of “waters of the United States” consistent with the Justice Scalia opinion (plurality standard) from Rapanos v. United States (2006). The EO instructed that any new proposed rule shall ensure that the Nation’s navigable waters are kept free from pollution, while at the same time promoting economic growth, minimizing regulatory uncertainty, and showing due regard for the roles of the Congress and the States under the Constitution.