Trump’s Clean Watershed: He orders the EPA to review Obama’s illegal waterways regulation.

Wall Street Journal Editorial, Updated Feb. 28, 2017 8:04 p.m. ET

Speaking of deregulation (see nearby), President Trump on Tuesday ordered the Environmental Protection Agency to reconsider an Obama Administration rule that seized control over tens of millions of acres of private land under the pretext of protecting the nation’s waterways. EPA chief Scott Pruitt will now follow due process to rescind one of his predecessor’s lawless rule-makings.

In 2015 the Obama EPA reinterpreted the Clean Water Act with a rule extending its extraterritorial claims to any creek, muddy farm field, ditch or prairie pothole located within a “significant nexus” of a navigable waterway. EPA defined significance broadly to include any land within the 100-year floodplain and 4,000 feet of land already under its jurisdiction, among other arbitrary delimitations.

Mr. Trump summed it up well, if not eloquently, when he said “it’s a horrible, horrible rule” and “massive power grab” that has “sort of a nice name, but everything else is bad.”

The rule would force farmers, contractors and manufacturers to obtain federal permits to put their property to productive use. After recent flooding in California, millions of more acres could come under EPA’s jurisdiction. Green groups could use the rule to block pipelines, housing projects or any development they don’t like. Farmers might be prohibited from using fertilizers that could flow downstream.

The Clean Water Act applies only to navigable waterways, but the EPA seized on the opening created by Justice Anthony Kennedy in the unfortunate 2006 Supreme Court case Rapanos v. U.S. that split 4-1-4. His controlling opinion invented the “significant nexus” standard that is a classic in judicial ambiguity and which the EPA used to expand government control over private property development.

Thirty-one states sued the EPA, and the Sixth Circuit Court of Appeals enjoined the rule nationwide in 2015 after finding that appellants were likely to win on the merits and that the rule-making was “facially suspect.” EPA even acknowledged that the “science available today” doesn’t support the regulation. Mr. Pruitt will be doing a national public service if he advises the Justice Department to withdraw the rule as an abuse of administrative power.