PORTLAND, Ore. — A lawsuit by a group of young people who say U.S. energy policies are causing climate change and hurting their future faces a major hurdle Tuesday as lawyers for the Trump administration argue to stop the case from moving forward.

Three judges from the 9th U.S. Circuit Court of Appeals are hearing arguments from lawyers for 21 young people and the federal government in Portland but are not expected to rule right away. The Obama and Trump administrations have tried to get the lawsuit dismissed since it was filed in Oregon in 2015.

“It’s just really disappointing to see the lengths that they go to — to not only not let us get the remedy that we’re seeking, but not even let us have the chance to prove our facts or present our case at trial,” said Nathan Baring, a 19-year-old from Fairbanks, Alaska, who joined the lawsuit when he was 15.

The lawsuit says the young are more vulnerable to serious effects from climate change in the future.

As the case drags on, sea ice that protects coastal Alaska communities from fierce storms is forming later in the year, leaving those villages vulnerable, Baring said Tuesday.

The young people argue that government officials have known for more than 50 years that carbon pollution from fossil fuels causes climate change and that policies promoting oil and gas deprive them of their constitutional rights to life, liberty and property.

Lawyers for President Donald Trump’s administration have argued that the lawsuit is trying to direct federal environmental and energy policies through the courts instead of through the political process.

“No federal court has ever permitted an action that seeks to review decades of agency action (and alleged inaction) by a dozen federal agencies and executive offices — all in pursuit of a policy goal,” the attorneys argued in a March court brief.

WATCH: Why climate change is an ‘all-encompassing threat’

Justice Department lawyers also assert that the young people had not identified any “historical basis for a fundamental right to a stable climate system or any other constitutional right related to the environment.”

The lawsuit says the young are more vulnerable to serious effects from climate change in the future. The American Academy of Pediatrics, 14 other health organizations and nearly 80 scientists and physicians agreed in a brief filed with the appeals court.

“Today’s children are expected to have poorer health as they age than today’s adults do, because of the worsening and intensifying effects of climate change,” three of the experts wrote in the New England Journal of Medicine.

They pointed out that the World Health Organization estimates that 88% of the global health burden of climate change falls on children younger than 5.

The lawsuit wants the U.S. District Court in Eugene, where the lawsuit was filed, to declare that the U.S. government is violating the plaintiffs’ constitutional rights by substantially causing or contributing to a dangerous concentration of carbon dioxide in the atmosphere.

It asks the court to declare federal energy policy that contributes to global warming unconstitutional, order the government to quickly phase out carbon dioxide emissions to a certain level by 2100 and mandate a national climate recovery plan.

The case has become a focal point for many youth activists, and the courtroom in Portland was expected to be packed Tuesday. A video livestream was being set up at a nearby park, where a rally was expected to be held, said Meg Ward, spokeswoman for Our Children’s Trust, a group supporting the lawsuit.

The U.S. Supreme Court last November declined to stop the lawsuit but told the Trump administration it could still petition a lower court to dismiss the case. A three-judge panel of the 9th Circuit granted the Trump administration’s motion to put the case on hold while considering its merits.

If the panel decides the lawsuit can move forward, it would go before the federal court in Eugene.