EUGENE – Attorneys for 21 young activists suing the federal government over climate change urged a judge Wednesday to allow their case to go to trial while government lawyers argued that a court can't direct national energy policy.

The youths -- from 10 states and ranging in age from 11 to 22 -- assert a constitutional right to a "climate system capable of sustaining human life.'' They contend the president and eight federal agencies have violated that right and the public's trust.

They've asked the court to order the government to prepare a "national remedial plan'' to phase out fossil fuel emissions, draw down excess atmospheric carbon dioxide and then monitor compliance.

Lawyers for the government argued that the federal court has no jurisdiction to prescribe what the president does in his official duties. Congress created the Administrative Procedure Act as the sole method to challenge actions taken by federal agencies, they said.

The youths want the court to violate the separation of powers by displacing Congress and the executive branch in adopting climate change policies, the government lawyers argued.

The issue should be decided by "political give and take'' and "not by one court,'' said Marissa Piropato, a trial attorney for the U.S. Department of Justice's natural resources section.

"They want this court to run or at least supervise several federal agencies,'' Piropato said to a standing-room-only crowd in U.S District Judge Ann Aiken's courtroom. "This is something the court cannot do.''

An overflow courtroom with a video feed was also full.

Lawyers for the group of children, teenagers and young adults argued it would be too "herculean, if not impossible" a task to individually challenge each of the thousands of federal agency actions that have caused injuries.

Court is the "last resort" to correct the "pervasive and systemic harms,'' said Julia Olson, one of their lawyers.

Federal agencies have violated the youths' right to due process over decades by promoting fossil fuel consumption, leasing lands for mineral development and permitting oil and gas wells, coal mines, pipelines and power plants, the plaintiffs' lawyer argued in court papers.

The government allowed the actions despite "long-standing knowledge of the resulting destruction to our nation and profound harm to future generations,'' they wrote.

Government lawyers called those claims a "novel assertion'' that lacks any support in the Constitution.

Olson responded: "The Constitution is silent on national energy policy, but it is loud on liberty. No branch of government has more responsibility than the court, especially in a case with children who have no political power. ... This generation has not faced a constitutional question greater than this one.''

Several of the young people, including lead plaintiff Kelsey Cascadia Rose Juliana, a 22-year-old student at the University of Oregon, attended the hearing.

Juliana said before court that she was buoyed by the support of others and that she felt Donald Trump's election to the nation's highest office gives the case "more gravity.''

The group filed the unprecedented case in federal court in Eugene in 2015 against President Barack Obama. It now names Trump, who has called climate change a "hoax.''

The plaintiffs said extreme weather events have harmed them. Jayden Foytlin of Louisiana said she missed a week of school after "floodwaters kept pouring in'' to her home in 2012 from weeks of rain. Others said they have suffered beetle-decimated forests, ocean warming, sea-level rise and decreased air quality.

"I often swam in the Indian River Lagoon on the west side of the barrier island, but I can no longer swim there because of increasing flesh-eating bacteria, dead fish and algae blooms,'' Levi Draheim of Florida wrote in a court declaration.

Olson spoke of Jaime Butler, a teenager who grew up on the Navajo Nation Reservation in Cameron, Arizona, but whose family had to move to Flagstaff because of severe drought. The family couldn't continue farming or harvesting medicinal plants, she said. Butler wrote in court papers that her family lost their "way of life'' over climate change.

It's not unheard for the courts to intervene when government policies violate rights, Olson said, pointing to cases involving public housing, school segregation, prison management and voting rights.

Government lawyers countered that school, housing or voting rights cases don't involve outside parties who might be contributing to alleged harms cited by plaintiffs.

The problem in this case is that climate change is a global problem and any remedies that the plaintiffs seek in the United State won't solve the issue, said Frank Singer, a Justice Department lawyer.

Attorney Andrea Rodgers, another lawyer for the youths, said the United States is by far the nation most responsible for the increase in global temperatures. "The federal government is the overwhelming cause and contributor to the greenhouse gas emissions causing injury to the plaintiffs,'' Rodgers said.

The government has lost earlier attempts to dismiss the case. On Monday, its lawyers filed a motion with the U.S. Supreme Court to put the case on hold, citing "defects'' in the "ill-conceived'' lawsuit and "egregious'' decisions by the judge in Oregon. The plaintiffs are preparing a response due next week.

The youths' lawyers offered to remove Trump from the suit without prejudice, meaning they could add him back at a later date. The government wants the president removed with prejudice, ending his involvement for good.

Judge Aiken said she'll issue a ruling soon on the government's motion to throw out the case.

-- Maxine Bernstein

mbernstein@oregonian.com

503-221-8212

@maxoregonian