President Trump has directed the Environmental Protection Agency and the Army Corps of Engineers to begin work on cancelling or rewriting an Obama administration rule that aimed to clarify federal authority over wetlands and other bodies of water. Construction industry groups welcomed Trump’s action; environmental organizations criticized it. But both sides agree it probably will be many months, perhaps a couple of years, until a revised rule is issued in final form. Even then, critics of that new regulation are sure to challenge it in court.

Trump on Feb. 28 signed an executive order that deals with a 2015 EPA-Corps rule that defines federally regulated “waters of the United States” (WOTUS). That regulation 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. Industry groups say the rule defined federal authority too broadly; environmental groups praised it as providing protection for waterways.

The same day that Trump signed the directive, EPA and Corps officials signed a notice stating they intended to “rescind or revise” the 2015 rule. Despite that quick initial action, 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.” Next, the agencies would have to issue a proposed rule and receive and review public comments on it. Then, the EPA and the Corps would publish a final version.

Goldman-Carter added, “That full process will almost certainly take at least one year and, more likely, closer to two years.”

Nick Goldstein, American Road & Transportation Builders Association vice president for regulatory affairs, says, “The EPA seems to be moving fast on this, but it is still a months-long, probably years-long process.”

ARTBA and other construction groups strongly criticized the 2015 WOTUS regulation. Goldstein says, “We think that the prior waters of the U.S. rule was highly overreaching, and we’re happy with the executive order.” For example, ARTBA has said the 2015 regulation did not categorically exclude roadside ditches from federal jurisdiction.

The 2015 WOTUS rule has not yet taken effect. Its critics convinced two federal courts to put the regulation on hold, pending further court action. In October 2015, a federal appellate court issued a nationwide stay on implementing the rule. Several weeks earlier, a federal district court judge issued a temporary injunction, which applied only in the 13 states that had sought that action.

The Trump administration’s new rule or rescission is expected to end up in court, too. Goldman-Carter 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.” Goldstein adds, “I fully expect there’ll be litigation.”