The Clean Water Act grants the federal government control over toxic discharges into “navigable water.” Imagine, then, the suprise of John Rapanos, who stands accused of violating the Clean Water Act because he dumped sand onto his own land. Nevermind that Mr. Rapanos’ land has been drained of standing water since the early 1900s. While it is not “navigable” and it is not “water,” says the Department of Justice, it is within the reach of federal environmental regulators. Why? Because of a risk that some grains of sand on his property may be carried by rainwater on an epic journey across drains, ditches, and creeks to the Kawkawlin River, a navigable body of water twenty miles away. Cato’s brief argues that government’s prosecution of Mr. Rapanos exceeds federal authority under both the plain text of the Clean Water Act and under the Commerce Clause.