WASHINGTON—The Supreme Court last week heard oral arguments in a landmark case that could determine the future of global warming liability litigation.

During the arguments, justices expressed skepticism about both parties' positions in American Electric Power Co. Inc. et. al. vs. State of Connecticut et. al., which some legal observers say indicates that the justices may be leaning toward tossing the suit because it is too unwieldy.

Experts have predicted a deluge of climate change litigation if the Supreme Court allows the underlying “public nuisance” lawsuit against greenhouse gas producers to proceed.

But even if the nation's highest federal court invalidates the suit, creative plaintiffs lawyers are expected to use the state courts to seek redress for damages from global warming.

The suit was filed in 2004 by a coalition of states, environmental groups and the city of New York against several of the nation's largest coal-burning utilities, alleging that their carbon dioxide emissions led to beach erosion, droughts and floods.

A New York federal judge dismissed the case in 2006 on grounds that the regulation of greenhouse gas emissions was a political question best left for the elected branches of government. However, in September 2009, the 2nd U.S. Circuit Court of Appeals reversed, sending shock waves through the energy industry.

Because of its potentially far-reaching implications, the Obama administration intervened in the case in August, filing a brief asserting that it was the job of the U.S. Environmental Protection Agency, and not the courts, to address greenhouse gas emissions.

All three participants in last week's oral arguments—Washington lawyer Peter D. Keisler, representing the utilities; acting U.S. Solicitor General Neal K. Katyal, representing the Obama administration; and New York Solicitor General Barbara D. Underwood, representing the states—faced tough questioning by the court.

While Messrs. Keisler and Katyal asked that the case be dismissed on the premise that it simply did not belong in the courts, especially because the EPA has begun to address climate change, that did not seem to be enough to sway the justices.

Justice Antonin Scalia said “the suit will just be brought in state court” if the Supreme Court rules there is no federal cause of action for global warming.

Some of the justices wanted to focus on whether the EPA was doing enough to “displace” such a lawsuit.

Chief Justice John G. Roberts Jr. suggested that perhaps the court should decide the case on its merits rather than on the narrow issue of administrative law.

Ms. Underwood received an equally cool reception when she asserted that litigation is the states' only remedy because the EPA has yet to act. She pleaded that the court not shut the doors to state nuisance lawsuits because of “something that is said to be imminent” but “may never happen.”

In response, Justice Ruth Bader Ginsburg said “the relief you are seeking...sounds like the kind of thing that EPA does...the relief you're seeking seems to me to set up a district judge...as a kind of super EPA.”

Justice Elena Kagan agreed that the lawsuit “sounds like the paradigmatic thing that administrative agencies do rather than courts.”

Justices Scalia and Samuel A. Alito expressed concern that allowing the state's suit to go forward would create a potentially infinite number of plaintiffs to litigate against an equally infinite number of defendants.

Several legal experts said they expect the Supreme Court to overturn AEP vs. Connecticut.

“If you were trying to read the tea leaves, the comments of Justices Kagan, Ginsberg and (Stephen) Breyer, each suggesting in different ways that greenhouse gas regulation is best left to the EPA, are particularly problematic for the plaintiffs, especially since these are justices whose support a successful environmental plaintiff would need to count on,” said William F. Stewart, a partner at Nelson Levine de Luca & Horst L.L.C. in Blue Bell, Pa.

“Each in their own way, Justices Alito, Scalia and Roberts expressed the view that, due to the ubiquitous nature of carbon emissions, and due to the magnitude of the challenge, courts are ill-equipped to address global warming,” said Mr. Stewart, who was not involved in the AEP case.

“It seems the Supreme Court probably will reverse the 2nd Circuit's decision. The court's reasoning is more difficult to predict, but victory for the petitioners seems likely,” said Richard Faulk, a partner at Gardere Wynne Sewell L.L.P. in Houston, who is not involved in the case but filed an amicus brief on behalf of several chemical, refining, manufacturing and insurer organizations.

“It does appear that the court will reverse the 2nd Circuit,” said John P. Krill Jr., a partner at K&L Gates L.L.P. in Harrisburg, Pa., who also filed an amicus brief.

Regardless of how the high court rules, legal experts expect climate change litigation to continue.

“It means we enter a new phase of the litigation. As some of the justices noted, someone will file a suit in a state court that has a more liberal interpretation,” said Mr. Krill.

“Tobacco cases were tossed for years and years, and ultimately they stuck,” said J. Wylie Donald, a partner in the Wilmington office of McCarter & English L.L.P. and chair of the firm's climate change and renewable energy practice.

“I wouldn't doubt the ingenuity of the plaintiffs bar....they are going to be looking for theories on how to get the compensation,” said Mr. Donald, whose firm was not involved in the case.

AEP vs. Connecticut is one of three closely watched cases in the area of climate change litigation, the other two being Native Village of Kivalina et al. vs. ExxonMobil Corp. (see related story) and Ned Comer et al. vs. Murphy Oil USA et al., filed by a group of Gulf Coast property owners who claim that oil and electric power companies' emissions “added to the ferocity of Hurricane Katrina” by contributing to global warming. The Supreme Court in January declined to hear Comer, which had been dismissed on the grounds that it presented a political question that could not be decided by the courts.