President Trump has signed an executive order requiring the Environmental Protection Agency and Army Corps of Engineers to begin a process to cancel or rewrite an Obama administration rule that aimed to clarify the scope of federal authority over wetlands and other bodies of water.

The directive, which Trump signed on Feb.  28, doesn’t immediately wipe from the books the 2015 EPA-Corps rule defining federally regulated “waters of the United States”—although the president and other critics of the regulation clearly are looking for a major revision, at a minimum.

The regulation, often called the WOTUS rule, is important for the construction industry, because it determines whether firms must get a Corps permit to deposit dredged or fill material in a particular waterway.

Under Trump’s order, EPA and the Corps must publish a new regulatory document to either rescind or change the 2015 rule. But the path to a final new water regulation is expected to be lengthy. Jan Goldman-Carter, National Wildlife Federation director for wetlands and water resources, noted that it took the Obama administration more than a year to discuss and formulate a proposal and another year to issue a final version.

Goldman-Carter said via email, "Even assuming a very expedited process, I expect it to take the EPA at least a few months to pull together a proposal and vet it through the interagency and other consultation processes." Then, officials would issue a proposed version of a rule and take and review public comments on it, before justifying a final regulation and publishing it. Goldman-Carter added, "That full process will almost certainly take at least one year, and, more likely, closer to two years."

Construction industry and other business groups have strongly criticized the WOTUS regulation, contending that it defined federal jurisdiction too broadly.

For example, the American Road & Transportation Builders Association said that the rule didn't categorically exclude roadside ditches from federal regulation but, instead, ARTBA said that EPA, "in a regulatory overreach, decided a litany of qualifications must be met before a roadside ditch can be deemed exempt from federal permitting requirements."

Granger MacDonald, chairman of the National Association of Home Builders, who attended the signing ceremony at the White House, said in a blog post, “This is an important first step towards fixing the flawed regulation and working towards a more sensible WOTUS rulemaking.”

Environmental groups strongly upport the 2015 rule. Rhea Suh, Natural Resources Defense Council president, called Trump’s action a “reckless assault.” She said, “Gutting this rule would threaten the wetlands and streams that feed the drinking water sources for one in three people—or 117 million Americans.”

The 2015 WOTUS rule has yet to take effect: two federal court rulings have put it on hold, pending further court action. In October 2015, a federal appellate court issued a nationwide stay on implementing the regulation. Several weeks earlier, a federal district court judge issued a temporary injunction regarding the rule, but limited it to the 13 states that had sought that court action.

A new Trump administration water rule may well spark further court action. Goldman-Carter of the National Wildlife Federation said, "We will participate actively in the administration’s rulemaking process and will certainly challenge a revised rule that rolls back protections for the nation’s wetlands, lakes, and streams."

Story corrected on March 3 to provide Jan Goldman-Carter's correct surname.