Three years ago, 16 youth climate activists decided to take the state of Montana to court, challenging a provision in a law that limits climate change considerations during environmental reviews of proposed fossil fuel projects. This week, they won. On Aug. 14, Judge Kathy Seeley of the Lewis and Clark County District Court in Helena, ruled in Held v. Montana that the current state law violates the youth plaintiffs’ right to a clean and healthful environment, a right spelled out explicitly in the state’s constitution. In a sweeping 103-page decision, Seeley also determined that climate change is hurting the young Montanans and that their injuries will grow with increasingly severe climate impacts.

“We are pretty over the moon,” said Melissa Hornbein, a senior attorney at Western Environmental Law Center who represented the activists, or plaintiffs.

Montana officials have already vowed to appeal. “This ruling is absurd,” Emily Flower, a spokesperson for Montana Attorney General Austin Knudsen, said in a statement that blamed the ruling on an “ideological judge.”

If it holds up against future challenges, the legal victory would be a big one for those pushing to strengthen climate action through the courts. The decision could influence other climate cases currently underway, environmental legal experts say, while also creating a roadmap for future lawsuits. It’s an important signal about the potential of climate litigation to move the ball forward on accountability for carbon emissions.

“I think this is the strongest decision on climate change ever issued by any court,” Michael Gerrard, founder and faculty director of Columbia Law School’s Sabin Center for Climate Change Law, wrote in an email to Bloomberg Green.

Benjamin Franta, a senior research fellow and head of the Climate Litigation Lab at the University of Oxford, said the decision is likely to be built upon. “As other branches of government continue to show inadequate action, the judiciary offers glimmers of hope for those seeking to halt the climate catastrophe unfolding before us,” he wrote in an email to Bloomberg Green. Here’s an overview of the case and what to expect going forward.

Youth plaintiffs in the climate change lawsuit, Held vs. Montana, arrive at the Lewis and Clark County Courthouse, on June 20 in Helena, Mont., for the final day of the trial. A Montana judge on Aug. 14 sided with young environmental activists who said state agencies were violating their constitutional right to a clean and healthful environment by permitting fossil fuel development without considering its effect on the climate. Thom Bridge/Independent Record via AP, File

What is this case about?

In 2020, a group of young Montanans filed a lawsuit challenging a state law that limits the scope of environmental reviews for proposed fossil fuel and other projects. At the time, the Montana Environmental Policy Act (MEPA) stated that actual or potential environmental impacts that are regional, national or global in nature could not be considered in governmental reviews of new projects. That effectively excluded the consideration of climate change.

In 2023, “the legislature made that even more explicit by saying that state agencies could not look at the climate change impacts of their actions in analyzing future projects,” said Hornbein. In May, Montana Governor Greg Gianforte signed that particular clarification to MEPA into law.

Both versions of the law, the activists alleged, violate the Montana constitution, specifically the section that says: “The state and each person shall maintain and improve a clean and healthful environment in Montana for present and future generations.”

State officials disagreed, arguing that Montana’s impact on global climate change is essentially nonexistent. The first youth-brought climate lawsuit to go to trial in the U.S., the court proceedings lasted eight days in June.

What did the judge’s ruling say?

Seeley delivered a win to the climate activists, ruling that the section of state law limiting the consideration of climate change in environmental reviews “violates Youth Plaintiffs’ right to a clean and healthful environment and is unconstitutional on its face.” She declared the new and older version of the state law “unconstitutional and permanently enjoined,” meaning it’s no longer in effect.

That was just one conclusion in a sweeping decision. Seeley also drew a clear line between Montana’s constitutional right to a clean and healthful environment and having a stable climate, according to Hornbein, noting “that the state has the authority (which it argued it does not) to deny permits for fossil fuel extraction and development to protect that fundamental right.”

The court essentially determined “that fossil fuel use is the principal cause of climate change, which is in turn causing serious health and environmental impacts that will continue to get worse,” Gerrard said. “The court found that renewables (wind, solar, hydro) can economically substitute for fossil fuels; that the youth plaintiffs have a right to a stable climate system under the right to a clean environment in the state constitution.”

A house sits in Rock Creek after floodwaters washed away a road and a bridge in Red Lodge, Mont., in June 2022. Young plaintiffs challenged the constitutionality of a Montana policy that does not require state agencies to consider the effect of greenhouse gas emissions in issuing permits for fossil fuel development, arguing the state is not doing enough to prevent climate change that leads to weather extremes. David Goldman/Associated Press

What does this decision mean for Montana?

In the near term, Montana’s climate-change-excluding environmental review policy is effectively null and void. This means state officials are now legally obligated to factor in the climate impacts of proposed projects they review. Long-term, the fate of the ruling is uncertain. Montana officials plan to appeal the decision, potentially sending the case all the way up to the state’s Supreme Court. Hornbein said her team is ready for that possibility.

What does this decision mean outside Montana?

Most immediately, Seeley’s decision may have the strongest impact on places where there’s a constitutional right to a healthy environment. At least six other states (Hawaii, Illinois, Massachusetts, New York, Pennsylvania and Rhode Island) “and around 150 other countries have a right to a healthy environment explicitly stated in their constitutions,” Gerrard said. “This ruling may inspire similar lawsuits around the world.” It could also have an impact on litigation already moving through the courts. “There is a case pending in Hawaii right now, which I think this order is heavily going to influence because there are similar constitutional provisions there,” said Hornbein.

She’s referring to Nawahine v. the Hawai’i Department of Transportation, in which 14 Hawaii youth, many of them indigenous, are alleging that the state prioritizes fossil-fuel-dependent transportation projects, such as new highways. Another youth-led climate lawsuit, Juliana v. U.S., initially filed in 2015, could also make its way to trial. In all of these cases, the youth plaintiffs are represented in part by the nonprofit public interest law firm Our Children’s Trust. In Montana, the youngest plaintiff was five years old.

“The plaintiffs’ lawyers very effectively put on the stand several young Montana residents who testified how they were personally affected negatively by climate change,” Gerrard said. “Putting a human face on this global problem worked well in this courtroom, and may well be followed elsewhere.”

Berkeley Law professor Daniel Farber’s characterization of the decision was more tempered. “This isn’t binding precedent, just a ruling by one trial judge in one state,” he said. “But it will certainly encourage other litigation and give other judges a little more comfort about ruling this way.”