Challenges to the controversial "Waters of the United States" rule should be heard by federal district, rather than appellate, courts, the U.S. Supreme Court said in a unanimous decision.

The decision, issued on Jan. 22, adds a layer of uncertainty to the Obama-era rule, which has been stayed by a federal appeals court since 2015, but could now go into effect before the Trump administration has a chance to rescind and replace it, though that is unlikely.

“This decision may lead to some confusion in the coming days and weeks,” the National Association of Home Builders (NAHB) said in a statement. “It’s conceivable that the 2015 rule could take effect in some states unless the courts, Congress or the agencies take action.”

NAHB says it will ask a federal district court in North Dakota to issue a nationwide moratorium against the 2015 rule. Other groups say they will work with the Trump administration to expeditiously repeal the rule and replace it with another, an effort that is already underway but that will likely take at least another year.

The Waters of the U.S (WOTUS) rule was a joint regulation issued by the U.S. Environmental Protection Agency and U.S. Army Corps of Engineers that sought to clarify which wetlands and streams were subject to federal regulatory jurisdiction, an issue that has been unclear following past Supreme Court rulings.

“Overall, it creates an immediate dilemma for EPA and the Department of Justice,” says Larry Liebesman, senior adviser with water-resources consulting firm Dawson & Associates. “Had the stay remained in effect, [the Trump administration] would have had a little more luxury on a proposed rescission and replacement.”

Opponents of the regulation, including construction interests and farmers, contend that it was an example of federal overreach.

In 2015, a U.S. District Court in North Dakota stopped the rule from going into effect in the 13 states that opposed it. The 6th U.S. Circuit Court of Appeals later found that it had jurisdiction and issued a nationwide stay of the rule, which has remained in place.

The National Association of Manufacturers challenged that jurisdiction of the case before the high court, arguing that litigation of the rule belonged in the U.S. district courts.

The lobby group, along with the National Association of Home Builders and the American Road & Transportation Builders Association. among others, said that Clean Water Act challenges should be heard at the federal district court level, closer to where regulation affects local projects and landowners. “Proceedings that begin in district court also have more possibilities for appeal, and therefore, a better chance at reaching a correct decision,” ARBTA said in a statement released Jan. 22.

In the Jan. 22 decision, written by Justice Sonia Sotomayor, the high court agreed that the clean water issues belong in district courts.

“The court acknowledges that, as the government argues, routing WOTUS rule challenges directly to the courts of appeals may improve judicial efficiency. But efficiency was not Congress’ only consideration,” Sotomayor wrote. “Had Congress wanted to prioritize efficiency, it could have authorized direct circuit-court review of all nationally applicable regulations, as it did under the Clean Air Act.”

NAHB says that in February the Supreme Court will issue a mandate to the Sixth Circuit that will result in the lifting of the nationwide stay of the WOTUS. NAHB says it will then ask the North Dakota district court to extend its initial injunction to all 50 states, from the 13 that opposed the regulation.

In the meantime, Liebesman advises those regulated under the Clean Water Act to look at guidance that was in effect before the WOTUS ruling, work with regulators, and expect some guidance from the district court\.