Hours before addressing a joint session of Congress for what was, in effect if not name, a State of the Union Address, President Donald J. Trump issued an Executive Order demanding a review of the controversial Waters of the United States Rule.

“It is in the national interest to 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,” the Executive Order, issued on Feb. 28, reads. It orders that the Environmental Protection Agency and the Army Corps of Engineers publish for notice and comment a proposed rule rescinding or revising the rule.

The agencies are ordered to consult with the U.S. Attorney General to facilitate decisions on whether to pursue or abandon any defense or prosecution before federal courts related to the rule.

The existing rule regulates the discharge of pollutants into “navigable waters,” defined as "the waters of the United States.” “The question of what is a "water of the United States" is one that has generated substantial interest and uncertainty, especially among states, small businesses, the agricultural communities, and environmental organizations, because it relates to the extent of jurisdiction for federal and relevant state regulations,” it says.

The scope of "waters of the United States," as defined by the prior regulations, has been subject to litigation in several U.S. Supreme Court cases, most recently in Rapanos v. United States (2006). In response to that decision, the agencies issued guidance regarding CWA jurisdiction in 2007, and revised it in 2008. The final rule took on the task of addressing definitional concerns.

“The Clean Water Rule ensures that waters protected under the Clean Water Act are more precisely defined, more predictably determined, and easier for businesses and industry to understand,” the EPS said at the time.

Specifically, the existing rule:

Defines and protects tributaries that impact the health of downstream waters.

Protects navigable waterways and their tributaries by determining that a tributary must show physical features of flowing water (a bed, bank, and ordinary high water mark) to warrant protection.

Protects waters that are next to rivers and lakes and their tributaries “because science shows that they impact downstream waters.”

Sets boundaries on covering nearby waters for the first time that are physical and measurable.

Limits protection to ditches that are constructed out of streams or function like streams and can carry pollution downstream.

The rule does not, according to an Obama Adminstration fact sheet: protect any types of waters that have not historically been covered by the Clean Water Act; add any new requirements for agriculture; interfere with or change private property rights; regulate most ditches; change policy on irrigation or water transfers; address land use; Include groundwater, shallow subsurface flow and tile drains.

The Trump Administration’s EPA, led by Administrator E. Scott Pruitt, swiftly issued a “Notice of Intention to Review and Rescind or Revise the Clean Water Rule” after the Executive Order was issued. “Through new rulemaking, the EPA and the Army seek to provide greater clarity and regulatory certainty concerning the definition of "waters of the United States,” Pruitt wrote.

The U.S. Chamber of Commerce is among the business groups applauding the move. “The 2015 rule was essentially a federal land grab,” says Senior Vice President of Environment, Technology, & Regulatory Affairs William Kovacs. “America’s businesses, farmers, and other land owners and managers will be happy to see it reconsidered and properly withdrawn under President Trump.”

The rule would have given the EPA and the Corps “unprecedented permitting and enforcement authority over land use decisions that Congress did not authorize,” he says. “To add insult to injury, the two agencies refused to properly assess the economic harm the rule would cause, despite the objections of Congress, States, businesses—even other federal agencies.”

The U.S. Chamber of Commerce—in addition to numerous other business associations and at least thirty states— filed lawsuits against the EPA and U.S. Army Corps of Engineers seeking to set aside the WOTUS regulation. The U.S. Court of Appeals for the Sixth Circuit Court put a nationwide hold on the regulation on Oct. 9, 2015.