The Supreme Court will weigh in on whether Boulder can continue with its climate accountability lawsuit in Colorado, or whether a federal court should hear the case. Justices heard oral arguments from both parties on Monday, October 5.
Both the city and county of Boulder sued fossil fuel companies ExxonMobil and Suncor Energy in 2018 over harms caused by greenhouse gas emissions that fuel climate change. That lawsuit was brought in state court, and the Colorado Supreme Court ruled that a state court could hear that case.
But the companies say that federal law prevents states from regulating greenhouse gas emissions, and that only the federal government can do that, therefore it should be heard by a federal court. That’s even as the Trump administration weakens the Environmental Protection Agency’s ability to regulate greenhouse gas emissions.
This summer, the EPA rescinded the 2008 Endangerment Finding, a rule that established that greenhouse gas emissions are harmful to public health and safety, giving the EPA the mandate to regulate them. The rescission means the federal government has effectively repealed its own ability to regulate greenhouse gas emissions.
During oral arguments, both conservative and liberal justices had questions about whether the Supreme Court should even be hearing this case.
“I understand that you have several other federal issues that you have raised that are still pending in the state court,” Justice Ketanji Brown Jackson said. “So why shouldn't we wait and hear all of these claims once the state courts are done with their federal considerations?”
If the Supreme Court decides this case is not in its jurisdiction, or it sides with Boulder, the case will go back to be heard in Colorado. But environmental advocates worry that if the court sides with fossil fuel companies, it will hurt other climate accountability lawsuits brought across the country.
“Does federal law prevent the suit that Boulder chose to fashion under Colorado law?” asked Sarah Harris, the principal deputy solicitor general for the United States. She argued on behalf of the federal government, which is supporting Suncor in this case.
“They're down the chain. ‘I'm injured in Colorado, therefore I can sue all of the oil producers for their conduct everywhere with no limit in sight. Is that okay?’ And the answer under federal law for many reasons is ‘no.’”
Kevin Russell, the attorney representing Boulder, says the Clean Air Act doesn’t give the EPA the authority to determine what the balance should be between pollution and economic activity.
“It is a much more precise mandate…that is limited to putting a cap on the amount of emissions from particular point sources,” he said. “It does not go forward to say that states cannot enact laws that have the indirect effect of raising the costs of fossil fuels and thereby reducing their use.”
Justice Samuel Alito recused himself from the case. Though he didn’t give a reason, he’s recused himself from climate-related cases before, due to his financial interest in fossil fuels.
The court will likely not issue a decision until spring of 2027.
Boulder shows its support from afar
While the attorneys gave oral arguments before the justices in Washington, D.C., a small crowd gathered outside of the Boulder County Courthouse, holding signs and expressing their support for the city and county as they pursue their lawsuit
“The U.S. Supreme Court is hearing, at this moment, the companies’ arguments to stop our case before we ever have our day in court,” said Boulder Mayor Aaron Brockett. “We are asking the court to let us have that day. Because this is not an abstract issue for Boulder, it is a daily reality for our community. People across Boulder have experienced the impacts of a changing climate, from hotter summers and extreme heat to drought, declining snowpack, worsening wildfire risk, and devastating fires.”
The Marshall Fire, the most destructive in Colorado’s history, tore through Boulder County in 2021, destroying over one thousand structures. Estimates put the costs to the community at over $2 billion.
“We deserve the opportunity to present the evidence and the opportunity to seek accountability for the harms that our communities are experiencing,” Brockett said. “Whatever happens in this case, the people here today are part of something bigger than this lawsuit. We are standing up for our community. We are standing up for our right to seek accountability, and we are standing up for generations who will inherit the decisions that we make today.”
Two of the students that signed onto an amicus brief in support of Boulder also spoke to the crowd.
“The Tenth Amendment states that part of the US Constitution says that any power not specifically given to the federal government belongs to the states,” said middle schooler Penny Seguin. “In my brief, I argue that this includes the power and duty to protect people like me from harms from fossil fuels, a legal idea that says some things like air and water belong to everyone and, and the government has an affirmative responsibility to protect them for present and future generations.”
“(Suncor and Exxon) must be held accountable, and we deserve to have our day in court and be heard, especially the youth that are going to have to deal with this for the rest of our lives,” added high schooler Muriel Soutiere.
Abby O'Brien of KGNU contributed to this report.
Copyright 2026 Rocky Mountain Community Radio. This story was shared via Rocky Mountain Community Radio, a network of public media stations in Colorado, Wyoming, Utah, and New Mexico, including Aspen Public Radio.
