Participants look at a screen showing a world map with climate anomalies during the World Climate Change Conference 2015 at Le Bourget, near Paris, on Dec. 8, 2015. (Stephane Mahe/Reuters)

Late last week, a federal judge denied a Trump administration move to prevent a major climate change lawsuit from going to trial. The case, being brought by 21 young people against the federal government, is now closer to a full-fledged trial that will pit the Trump administration against children and young adults who insist the government is undermining their future through climate change inaction.

It’s a “very significant” decision, according to chief counsel for the plaintiffs, Julia Olson, executive director of advocacy group Our Children’s Trust. “This allows us to keep moving forward to trial.”

The case, which was originally filed against the federal government during the Obama administration, alleges that the government violated the plaintiffs’ constitutional rights by promoting the production of fossil fuels and the emission of greenhouse gases — harming a climate system that they argue the government has a legal responsibility to protect for the public good. The plaintiffs range in age from 9 to 21.

The lawsuit has since been inherited by the Trump administration, which assumed the role of defendants by default after the January presidential inauguration.

The potential implications of the lawsuit — the first of its kind to be filed in the United States — are immense. Should the plaintiffs prevail, legal experts have pointed out that the case could set a precedent for an entirely new type of environmental litigation, suggesting that citizens do have a constitutional right to a healthy climate. In this case, the federal government would probably be ordered to take concrete action against the progression of climate change, for instance by reducing domestic greenhouse gas emissions by a set amount over a given period of time.

These implications are perhaps even greater now that President Trump has announced his intent to withdraw from the Paris climate agreement. When the announcement was made, Olson issued a statement suggesting that the courts may still provide a means of forcing the federal government to act on climate change.

“We believe that courts, including the U.S. District Court in Oregon, as a coequal branch of government, can and will use judicial oversight to ensure the executive branch is complying with its constitutional and public trust obligation to implement a climate recovery plan,” she said in the statement. “And unlike the Paris Agreement, the Trump Administration cannot withdraw from this lawsuit.”

The case cleared its first major hurdle in November 2016, when U.S. District Judge Ann Aiken denied motions by the federal government and industry trade groups to have the case dismissed, clearing it to proceed to trial. However, the defendants then turned to the U.S. Court of Appeals for the 9th Circuit, filing a motion to have this ruling overturned.

The final decision on whether this appeal could take place remained in Aiken’s hands.

Last month, U.S. Magistrate Judge Thomas M. Coffin recommended a denial of the appeal, and this week Aiken officially denied the motion, once again clearing the case to go to trial. Aiken stated in her decision that she agreed “certification for interlocutory appeal is not warranted in this case.”

However, the plaintiffs may face additional challenges yet before they get there.

On Friday, the Trump administration filed a petition with the 9th Circuit seeking a rarely invoked legal procedure called a writ of mandamus, in which a higher court would step in and review Aiken’s original decision to deny the defendants’ motion to dismiss.

“Writs of mandamus are very rare, and they’re even more rarely granted,” said James May, a professor of law and chief sustainability officer at Widener University, who is not involved in the lawsuit. “Because what they do is they intrude on the province of the district court’s proceedings.”

According to May, a writ of mandamus is an “extraordinary and unusual” move, and when it’s granted it’s almost always used to prevent a trial court from inappropriate conduct.

“The argument would be that, in essence, the lower court has gotten something so wrong that there would be harm to the parties and it would be an affront to the rule of law for the case to proceed where it stands,” he told The Washington Post.

The decision on whether to grant the writ of mandamus will reside with the 9th Circuit, rather than the district court. But May added that even if the appeals court took the unusual step of allowing the review, it doesn’t mean it will ultimately reverse the district court’s decision.

“To me, the fact that they are doing this really shows how worried they are about going to trial in this case,” Olson said.

Whether the federal government makes the move, and what will happen afterward, remains to be seen. In the meantime, the industry trade groups’ requests to withdraw from the case are also still pending a decision from the court.

And meanwhile, according to Olson, “we’re still on fast-track to trial.”