President Barack Obama’s flagship policy on climate change had its day in court on Tuesday, September 27, before the full D.C. Appeals Court.

The international community closely watches. Most Americans, however, remain unaware of the historic case known as the Clean Power Plan (CPP), which, according to David Rivkin, one of the attorneys arguing against it, “is not just to reduce emissions, but to create a new electrical system.”

The oral argument phase allows the judges to interact with lawyers from both sides and with each other—typically allowing a maximum 60-90 minutes to hear both sides and occasionally, with an extremely complex case, will allow two hours. However, for the CPP, the court scheduled a morning session focusing on the EPA’s authority and an afternoon session on the constitutional claims against the rule—which ended up totaling nearly 7 hours. Jeff Holmstead, a partner with Bracewell Law, representing one of the lead challengers, told me this was the only time the full court has sat all day to hear a case.

One of the issues addressed was whether the EPA could “exercise major transformative power without a clear statement from Congress on the issue”—with the 2014 Utility Air Regulatory Group (UARG) v. EPA determining it could not. Republican appointee Judge Brett Kavanaugh noted that the UARG scenario “sounds exactly like this one.”

Judge Thomas Griffith, a Bush appointee, questioned: “Why isn’t this debate going on in the floor of the Senate?” In a post-oral argument press conference, Senator James Inhofe (R-OK) pointed out that the debate has been held on the Senate floor in the form of cap-and-trade legislation—which has failed repeatedly. Therefore, he said, the Obama administration has tried to do through regulation what the Senate wouldn’t do through legislation.

“Harvard law professor Laurence Tribe, one of Obama’s mentors,” writes the Dallas Morning News: “made a star appearance to argue that the Clean Power Plan is unconstitutional.”

Judge Karen LeCraft Henderson, a Bush appointee, concluded: “You have given us all we need and more, perhaps, to work on it.”

The day in court featured many of the nation’s best oral advocates and both sides feel good about how the case was presented.

For the challengers (who call CPP “an unlawful power grab”), West Virginia Attorney General Patrick Morrisey, who along with Texas AG Ken Paxton, co-lead the case, reported: “We said (then) that we were looking forward to having our day in court on the merits. Today was that day. I think that the collective coalition was able to put very strong legal arguments forward, as to why this regulation is unlawful, and why it should be set aside.”

But the case has its proponents, too, and they, also, left feeling optimistic. In a blog post for the Environmental Defense Fund, Martha Roberts wrote about what she observed in the courtroom: “The judges today were prepared and engaged. They asked sharply probing questions of all sides. But the big news is that a majority of judges appeared receptive to arguments in support of the Clean Power Plan.” She concluded that she’s confident “that climate protection can win the day.”

The Wall Street Journal (WSJ) summarized the session saying that stakeholders on all sides were left “parsing questions and reactions, and searching for signs of which way the judges are leaning.” U.S. News reported: “The judges repeatedly interrupted the lawyers for both sides to ask pointed questions about the legal underpinnings of their positions.”

The decision, which is not expected for several months, may come down to the ideological make-up of the court: 6 of the judges were appointed by Democrat presidents and 4 by Republicans. Though, according to WSJ, Obama appointee Judge Patricia Millet “expressed concern that the administration was in effect requiring power plants to subsidize companies competing with them for electricity demand.” She offered hope to the challengers when she said: “That seems to be quite different from traditional regulation.” Additionally, in his opinion published in the Washington Post, Constitutional law professor Jonathan Adler, stated: “Some of the early reports indicate that several Democratic nominees posed tough questions to the attorney defending the EPA.”

Now, the judges will deliberate and discuss. Whatever decision they come to, experts agree that the losing side will appeal and that the case will end up in front of the Supreme Court—most likely in the 2017/2018 session with a decision possible as late as June 2018. There, the ultimate result really rests in the presidential election, as the current SCOTUS make up will be changed with the addition of the ninth Justice, who will be appointed by the November 8 winner—and that Justice will reflect the new president’s ideology.

Hillary Clinton has promised to continue Obama’s climate change policies while Donald Trump has announced he’ll rescind the CPP and cancel the Paris Climate Agreement.

The CPP is about more than the higher electricity costs and decreased grid reliability, which results from heavy reliance on wind and solar energy as CPP requires, and, as the South Australian experiment proves, doesn’t work. It has far-reaching impacts. WSJ states: “Even a partial rebuke of the Clean Power Plan could make it impossible for the U.S. to hit the goals Mr. Obama pledged in the Paris climate deal.” With Obama’s climate legacy at stake, the international community is paying attention.

And Americans should be. Our energy stability hangs in the balance.

The author of Energy Freedom, Marita Noon serves as the executive director for Energy Makes America Great Inc., and the companion educational organization, the Citizens’ Alliance for Responsible Energy (CARE). She hosts a weekly radio program: America’s Voice for Energy—which expands on the content of her weekly column. Follow her @EnergyRabbit.