If the U.S. Supreme Court takes up a high-profile case over whether states can invoke common law to force industry to reduce greenhouse gas emissions, it's likely one of the justices will sit on the sidelines.
The justices are due to announce Monday whether they will hear the case, American Electric Power v. Connecticut.
When they do reveal their plans, there is a strong likelihood that Justice Sonia Sotomayor will announce that she is recusing herself.
That is because, prior to her nomination in 2009, she served on the appeals court panel that heard the case, although she did not participate in the ruling itself.
A Sotomayor recusal could have a major impact on how the case is resolved if the justices choose to take the case, legal experts say, with one possibility being a 4-4 deadlock among the remaining eight justices.
The case, one of three around the country on the issue, focuses on the attempts of eight states, New York City, and several land trusts to force six companies that operate fossil fuel-fired electric power plants to reduce emissions via federal "public nuisance" common law.
The plaintiffs' argument is that by contributing to global warming, the power companies are contributing to a public nuisance under federal common law. Therefore, the states say, they can seek injunctive relief that would require the defendants to reduce their emissions.
The power companies, including American Electric Power Co. Inc., argue, among other things, that the Clean Air Act supplants the federal common law in the carbon emissions area. In other words, it is up to U.S. EPA to regulate greenhouse gases, they argue.
The Obama administration agrees, up to a point. Acting Solicitor General Neal Katyal has asked the court to send the case back to the appeals court "in light of multiple actions that EPA has taken" since the original ruling was issued.
If the Supreme Court takes the case, it would be the biggest environment issue before the court since the 2007 decision in Massachusetts v. EPA, in which the court held that the Clean Air Act could be used to regulate carbon emissions.
If the court decides against intervening, it could still take up the issue at a later date when the other two cases comes before the justices.
In the case currently under consideration, the New York-based 2nd U.S. Circuit Court of Appeals heard arguments in June 2006, with Sotomayor a member of the three-judge panel.
But, unusually, the court did not issue its ruling until September 2009, just after Sotomayor was confirmed to her position on the Supreme Court. The court ruled in favor of the states.
A footnote in the opinion said that the two remaining members of the panel "had determined the matter."
"I find it inconceivable Justice Sotomayor would not be expected to recuse," said Jonathan Adler, a professor at Case Western Reserve University School of Law who specializes in environmental law.
Even though Sotomayor was not involved in the final decision, she would at least have been involved in discussions about it before leaving the 2nd Circuit, he added.
Sotomayor may have set a precedent when she recused herself in similar circumstances.
In a case called Arar v. Ashcroft, concerning the George W. Bush administration's rendition program, she was still serving on the 2nd Circuit when arguments were heard but did not participate in the decision.
Although the Supreme Court, now with Sotomayor among its ranks, did not end up hearing the case, the court noted in rejecting the petition that Sotomayor didn't participate in the discussion.
Massachusetts v. EPA looms over the current case in part because it was a 5-4 decision, with regular swing vote Justice Anthony Kennedy joining the liberal wing of the court.
In reading the tea leaves, court-watchers wonder if there could be a similar split this time around.
Sotomayor, who replaced Justice David Souter in 2009, was not on the court then. Neither was Justice Elena Kagan, who succeeded Justice John Paul Stevens this year. Both might be expected to vote with the liberal justices.
If the other members of the court voted upon similar lines as they did in 2007, it would again be a 5-4 split. But if Sotomayor is recused, it would be 4-4.
That would leave the 2nd Circuit ruling in favor of the states intact, but the case would not be binding upon other federal courts of appeal.
If Sotomayor is recused, "it's much more difficult for environmental groups to get a precedential victory," Adler noted.
Another possible outcome is a 5-3 split, with Kennedy joining the conservative justices. In that scenario, Sotomayor's noninvolvement would not be decisive.
Raymond Ludwiszewski, a lawyer at the Gibson Dunn & Crutcher law firm, who has filed an amicus brief on behalf of the Association of International Automobile Manufacturers, said he is not convinced whether votes in Massachusetts v. EPA will have much relevance.
"I wouldn't necessarily see Massachusetts v. EPA as a touchstone," he said, in part because the justices may be more fixated on the underlying federal common law issues.
Further confusing the matter, there is also an outside chance that Kagan could recuse herself due to her previous position as solicitor general, the Obama administration's top legal advocate.
Kagan was confirmed to her new position in early August, just before the government told the court it wanted to file a brief in support of the power companies. It is not clear whether she had any involvement in the case before it reached the Supreme Court.
Kagan effectively stood down from her role as solicitor general in May, when Katyal took over as acting solicitor general. That was before the power companies filed their initial petition seeking Supreme Court review.
'Too hard to handicap'
As for whether the court will take up the case, Ludwiszewski noted that the prospect of Sotomayor's recusal and the possibility of a 4-4 split might persuade the justices against taking it, especially as they could wait for one of the other two cases on the same question.
"It's the sort of case that they should be attracted to," he said. "But it's too hard to handicap."
As Katyal noted in the government's brief, "key features in this case counsel against" the court taking up the matter, including the fact that, as yet, there is no split among the federal appeals courts.
Of the other two cases, one, Kivalina v. Exxon Mobil Corp., is in the 9th U.S. Circuit Court of Appeals and is yet to be argued. The other, Comer v. Murphy Oil, was initially decided in favor of the plaintiffs by the 5th U.S. Circuit Court of Appeals.
In a strange twist, the ruling was vacated after the court moved to rehear the case but then realized there was no quorum after several judges had to recuse themselves.
David Doniger, policy director of the Natural Resources Defense Council and a member of the plaintiffs' legal team in the American Electric Power case, agrees that it should not be assumed that the court will take the case.
Sotomayor's possible recusal would not be significant on that point because only four votes are required for the court to decide to hear a case and "she would not likely be one of the ones in favor," he said.
"There are various reasons why it would be inappropriate or not urgent to take the case now," he added.