On June 4th, in a packed courtroom in Portland, Oregon, Judge Andrew Hurwitz, of the United States Court of Appeals for the Ninth Circuit, posed an unusual hypothetical question. “Assume that we have rogue raiders come across the Canadian border of the Northwest. They are kidnapping children of a certain age and murdering them,” he said. “The White House refuses to do anything and Congress doesn’t act. Can those people”—the terrorized families and communities—“go to court to compel action?” He was asking Jeff Clark, the lawyer representing the federal government, the defendant in the case. Clark replied, “My answer is no.”

Judge Hurwitz, along with Judges Mary Murguia and Josephine Staton, was presiding over oral arguments in Kelsey Cascadia Rose Juliana v. the United States, better known as the climate kids’ lawsuit. In August of 2015, the twenty-one plaintiffs, who then ranged in age from eight to nineteen years old, sued the Obama Administration and various federal agencies, alleging that the government’s policies on fossil fuels advanced catastrophic climate change and therefore violated the right, guaranteed to them under the Fifth Amendment, that no one shall be “deprived of life, liberty, or property, without due process of law.” In other words, as Judge Hurwitz’s hypothetical suggested, their suit is an attempt to compel action from a government that is ignoring (and furthering) a life-threatening danger that they face. Since then, the case has ricocheted through the courts, gaining strength as urgency around climate change has increased and the Trump Administration has continued to deny that a problem exists. (“The climate goes both ways,” President Trump said in London, last week. “I believe that there’s a change in weather and I think it changes both ways.”) Instead, the Administration has aggressively promoted and expanded the use of fossil fuels, recently announcing that natural gas would be rebranded as “freedom gas.”

Hurwitz asked his question at the start of the hearing, establishing the stakes and reflecting the gravity with which the judges were weighing the plaintiffs’ claims. It pointed to an issue at the heart of the case, and at the heart of most climate litigation—the separation of powers. “The central issue the Ninth Circuit is grappling with is what is the role of the courts vis a vis Congress and the executive branch,” Michael Gerrard, a professor at Columbia Law School and the faculty director of the Sabin Center for Climate Change Law, wrote me in an e-mail. “If a building is on fire and all the firefighters are off at a convention, can the neighbors break into the firehouse and run the firetrucks themselves? Or do they have to wait for permission, while the building burns down? Likewise, if the planet is on fire and Congress and the Administration are checked out, can the courts act on their own?”

Since most major environmental statutes date to the nineteen-seventies, and Congress has not been able to pass a single major environmental law since 1990, the Environmental Protection Agency, other federal agencies, and the courts have been forced to address current problems with laws that are decades old. (The main problem now is that the Senate will not act. In early May, as the House prepared to vote on a new bill, the Climate Action Now Act, which would force the Trump Administration to remain in the Paris climate agreement, the Senate Majority Leader, Mitch McConnell, said that it would “go nowhere.”) Once Trump was elected, and federal agencies no longer had a mandate to address climate change, the courts became the only branch of government where action might be possible. But, in the absence of adequate climate-policy laws, the courts must find their right to act in the Constitution. Two days after Trump’s election, a federal judge for the District of Oregon, Ann Aiken, found that right and issued a major decision, denying the government’s motion to dismiss the Juliana case. “Where a complaint alleges governmental action is affirmatively and substantially damaging the climate system in a way that will cause human deaths, shorten human lifespans, result in widespread damage to property, threaten human food sources, and dramatically alter the planet’s ecosystem, it states a claim for a due process violation,” Aiken wrote. “I have no doubt that the right to a climate system capable of sustaining human life is fundamental to a free and ordered society.” A trial date was set for early last year, then postponed until last fall. The government, meanwhile, turned to the Supreme Court, asking the Justices to prevent the trial from going forward. In November, they declined to do so, determining that the government needed to bring its objections before the Ninth Circuit first. The Ninth Circuit now must decide whether the case can, finally, proceed to trial.

During the hearing, Jeff Clark, from the Justice Department, argued that there is no substantive constitutional right to a stable environment. Julia Olson, the co-lead attorney for the plaintiffs and the executive director of Our Children’s Trust, a group that has been bringing climate-litigation cases around the country, argued that the government misunderstood the plaintiffs’ claims. She said, “The Supreme Court has already recognized that the liberties that we all hold include our right to bodily integrity and personal security and family autonomy. So this court doesn’t need to step out of bounds and recognize any kind of new right, it can stick with the bedrock fundamental rights that we all—” At this point, Judge Hurwitz interrupted her, saying, “Actually, to be fair, you’re arguing for us to break new ground.” He added, “I’m sympathetic to the problems you point out, but you shouldn’t minimize—you shouldn’t say this is just an ordinary suit, and all we have to do is follow A, B, and C, and we get there. You’re asking us to do a lot of new stuff, aren’t you?” Olson replied, “We’re asking the court to apply bedrock constitutional law and principles to a wholly new set of facts.”

The government, for its part, disputed some of those facts. Judge Aiken had found that the plaintiffs had standing to sue because they had demonstrated three things: that they had suffered particular, concrete injuries; that the cause of their injuries was “fairly traceable” to the government’s actions; and that the courts had the ability, at least partially, to remedy these injuries. On the first two parts of standing, the government’s case is weakening by the minute, owing especially to the growing body of attribution science—studies published in peer-reviewed journals that directly link extreme weather events, such as huge hurricanes and raging wildfires, to climate change. “Evidence to meet the standing burden has gotten much stronger,” Ann Carlson, an environmental-law professor at U.C.L.A., told me.

All the plaintiffs were in the courtroom for the hearing. They have each submitted sworn testimony to the court, explaining the personal injuries that climate change has caused in their lives. The youngest, Levi Draheim, who is now eleven, lives in the barrier-island community of Satellite Beach, Florida, which his family has been forced to evacuate several times, due to hurricanes and floods. Jayden Foytlin, who is fifteen and lives near the Louisiana coast, suffered emotional trauma when her home was severely flooded in 2016 and 2017. In her testimony, she describes how her family, having nowhere else to go, slept in the living room in a “house that was full of sewage and flood water damage.” Journey Zephier, nineteen, of Hawaii, has watched treasured coral reefs near his home die, due to ocean acidification and warming temperatures, and last year saw his home flood when an unprecedented fifty inches of rain fell in less than twenty-four hours, which also caused landslides and power outages in his community. Jamie Butler, eighteen, had to leave her home and her relatives in the Navajo Nation, because of severe drought and water scarcity. Kelsey Juliana, the lead plaintiff (and the oldest, at twenty-three), grew up in Eugene, Oregon, where she is now an environmental-studies major at the University of Oregon. She, along with eight of the other plaintiffs, described adverse health impacts from the wildfires that rage in and around their home towns practically every year. Some also wrote about the damage that extreme weather events and climate threats have caused to their cultural heritage; others described psychological troubles—nightmares, anxiety, depression.