A Trump administration move to delay the implementation date of an Obama-era Clean Water rule has sparked a new legal battle.

Under a decision published on Feb. 6 in the Federal Register, the “waters of the U.S.,” or WOTUS, rule won’t be applicable until Feb. 6, 2020. By that date, the Environmental Protection Agency and Army Corps of Engineers expect to have repealed and replaced the 2015 rule with a new, less expansive one.

But hours after the Federal Register published the finalized delay, a number of  lawsuits were filed against the action. A suit filed by the Southern Environmental Law Center on behalf of American Rivers and eight other environmental groups claims the EPA and Corps violated long-standing law by altering “basic environmental safeguards without giving the public notice and a chance to weigh in.”

According to the Natural Resources Defense Council and the National Wildlife Federation, which filed a second suit, the addition of an “applicability date” to delay the implementation of the rule occurred in a “rushed and illegitimate process.” The agencies have 60 days to respond to the suits. Attorneys general from 11 states, including California and New York, also filed suit in federal court, challenging the suspension of the rule.

In announcing the delay, EPA Administrator Scott Pruitt in a statement said the agency was “taking action to reduce confusion and provide certainty.” The action is aimed at thwarting the possibility that WOTUS could be implemented in some states but not others, following a Jan. 22 U.S. Supreme Court decision that lifts a nation­wide stay of the rule.

Randy Noel, chairman of the National Association of Home Builders, welcomed the delay announcement, saying, “This is a decision we have been waiting a long time for.”

The 2015 rule would have required builders and developers to obtain federal permits for activities in isolated ponds, dry streambeds and most ditches.

But the action is, “in certain respects … a risky strategy,” says Larry Liebesman, a senior adviser with water-resource consulting firm Dawson & Associates. The term “applicability date,” which does not appear in the original WOTUS rule, is one sticking point. Liebesman says a judge may find the use of the phrase “applicability date” to be reasonable, considering the consequences of a rule that would be applied inconsistently across the U.S. On the other hand, a judge may rule the EPA and Corps exceeded their scope by inserting the new term into the regulation, he says.

Liebesman expects EPA and the Corps are “doing all they can to prevent the 2015 rule from going into effect.” He expects that the agencies will ask a federal district court in North Dakota to expand to all 50 states the court’s earlier 13-state stay. Pruitt has said a new rule will be finalized this year. But, since the agencies have not yet formally withdrawn the 2015 rule, Liebesman says that timeline might be ambitious.