The U.S. Supreme Court has dipped into a controversial 2015 regulation that sets the scope of federal regulation of waterways. On Oct. 11, it heard oral arguments on whether legal challenges to that rule, which defines federally regulated “waters of the United States” under the Clean Water Act, must be brought before federal district courts or federal appeals courts. [Read oral argument transcript here.]

Issued by the Army Corps of Engineers and the Environmental Protection Agency during the Obama administration, the regulation has been the center of a fierce dispute. Construction and other business groups contend the rule broadens federal authority too much. Environmental organizations say it provides proper protection against water pollution.

But the case before the high court, National Association of Manufacturers v. U.S. Dept. of the Army, doesn’t deal with the merits of the rule itself. It focuses on a much narrower procedural issue. As attorney Timothy S. Bishop, representing NAM, put it, the case is an example of “litigation over where to litigate.”

The Clean Water Act lists seven types of activities for which cases should be brought to appellate courts, and NAM says challenges to the water rule aren’t among them. Instead, it argues that challenges to the waters-of-the-U.S. rule should go to district courts. The Justice Dept. and environmental groups contend the Clean Water Act indicates the suits should be filed in appellate courts.

Nick Goldstein, American Road & Transportation Builders Association vice president for regulatory affairs, says filing a case in district court “gives you more chance to get things right.” Larry Liebesman, senior adviser with water-resources consulting firm Dawson & Associates, says, “Arguably, you might at the end of the day get a better result by having different courts looking at the same record from a different perspective.”

Goldstein notes that, if a party takes a case directly to an appeals court and doesn’t win, its further options are limited. “If you lose at the appellate level, then it’s the Supreme Court or bust,” he says.

How might the justices rule? A former senior trial attorney with the Justice Dept. environmental division, Liebesman says, “I think there were tough questions on both sides, and I certainly will say that it’s not clear-cut 100%.” But judging from questions from justices who might be viewed as supporters of the government’s arguments, they seemed to favor the NAM side, “based on a narrow reading of the [Clean Water Act] actions subject to appellate review,” he says.

Status of the Rule

The water rule itself hasn’t taken effect. Its critics scored a win in October 2015, when the 6th U.S. Circuit Court of Appeals issued a nationwide stay of the rule. On another front, in June, the Trump administration proposed rescinding the 2015 regulation. It plans to draft a new one that almost certainly would be a pullback from the earlier version.

A couple of the justices asked whether the NAM case would become moot when the Trump administration releases its new water rule. Representing the government’s side, Rachel P. Kovner, assistant to the solicitor general, said if the 2015 rule were canceled, the same issue—where to litigate—was likely to arise again for the new version of the rule.