Supreme Court Justice Ruth Bader Ginsburg asked probably the most obvious question at Wednesday's oral arguments on the Obama administration's Waters of the U.S. rule: With Trump in office, isn't the matter moot?

"May I just ask you a question about if, as seems likely, the rule, the 'waters of the United States' definitional rule is rescinded, is this case moot?" the liberal justice asked a lawyer representing industry opponents of the rule.

"Well, I think it's just too early to say when or if it will be rescinded, Justice Ginsburg," Timothy Bishop replied, explaining that the Environmental Protection Agency wrapped up the public comment period on its review of the Waters of the U.S. rule on Sept. 27. "There were thousands of [comments]. We don't know what the timetable is. We don't know what the government will do."

Wednesday's oral arguments were over the narrow issue of court jurisdiction for lawsuits opposing the rule. It is not clear if a lower district court should be given primacy in ruling on the water rule or if it can go straight to a federal appeals court.

The 6th Circuit Court of Appeals had stayed the regulation until the issue is worked out at the Supreme Court, which heard National Association of Manufacturers v. Department of Defense on Wednesday.

"But ... the notice, as I understand it, notice and comment period has concluded," Ginsburg responded.

Bishop answered that it has, but "we don't know" if the Trump administration "will rescind the rule or not." The one thing that is "clear" is that environmental groups are ready to sue immediately if the EPA decides to withdraw the rule, the lawyer added. "And I would suggest that while that challenge, doubtless with a stay request attached, is pending, then the fate of the WOTUS rule is still up in the air."

EPA Administrator Scott Pruitt has said that he plans to roll back the rule.

Liberal Justices Sonia Sotomayer and Elena Kagan focused their questions on the technical nature of when a case becomes the business of an appeals court, rather than a district court, to take up a regulatory matter such as the water rule. They asked about how water permits are issued, whether and how a permit under the Clean Water Act becomes contestable, and the jurisdiction of federal appeals courts.

Chief Justice John Roberts appeared to disfavor allowing district courts to take up the rule, saying it would result in judicial inefficiency. The industry plaintiffs in Wednesday's case favor the district courts taking up the lawsuits.

"... [O]ne of the consequences that your opponent [the federal government] points out is that if you're correct and these actions are brought in the district court, each of the district courts will have to review the entire administrative record, and presumably, you could have dozens of the district courts engaged in that same activity, and then it would have to be done all over again when you get to the court of appeals," Roberts said.