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Youth activists in the United States’ Montana who won a landmark constitutional climate case against their government in 2023 are back in court, seeking to block new laws they say undermine their right to a clean and healthful environment.
Lawyers representing 13 of the 16 original plaintiffs in Held v State of Montana filed a petition for original jurisdiction with the Montana Supreme Court on December 10, 2025. The case asks the court to enforce its earlier judgment and strike down three environmental laws passed earlier this year.
The petition names the state of Montana, Governor Greg Gianforte and the Montana Department of Environmental Quality (DEQ) as respondents. It challenges House Bills 285 and 291, and Senate Bill 221, all passed by the Montana legislature and signed into law by the governor. The measures came into force in May 2025.
The plaintiffs argue that the laws unlawfully restrict environmental reviews under the Montana Environmental Policy Act (MEPA). According to the petition, the legislation narrows the definition of a “proposed action” and limits environmental assessments to “proximate” impacts.
“Such restrictions on the scope of environmental reviews under MEPA require agencies to turn a blind eye to known environmental harms caused by fossil fuel projects and greenhouse gas emissions,” the petition stated.
The new legal action follows a major ruling in December 2024, when the Montana Supreme Court upheld a lower court decision in Held vs Montana. The court found that the state had violated the Montana Constitution by barring regulators from considering greenhouse gas emissions or climate impacts during environmental reviews conducted under MEPA.
That decision affirmed a ruling by Judge Kathy Seeley of the Lewis and Clark County District Court in August 2023. She had ruled in favour of 16 youth plaintiffs, who argued that state policies promoting fossil fuel development violated their constitutional rights.
“By prohibiting analysis of GHG emissions and corresponding impacts to the climate, as well as how additional GHG emissions will contribute to climate change or be consistent with the Montana Constitution, the MEPA Limitation violates youth plaintiffs right to a clean and healthful environment and is unconstitutional on its face,” the August 14, 2023 order said.
In response to that court victory, the state moved to amend the law. On May 1, 2025, Governor Gianforte signed five bills affecting environmental regulation, saying the changes were necessary “to protect the environment, cut red tape, and provide certainty to businesses and Montana’s energy sector”.
“Last year, the Montana Supreme Court issued a series of rulings that if left unchecked would have impacted Montana’s energy sector at time when Americans have seen electricity costs soar nearly 30 percent in the last four years,” Gianforte said. “This package of legislation reduces red tape and provides certainty to small and large businesses across our state”.
Supporters of the legislation argue it restores MEPA to its original purpose. Montana House Speaker Brandon Ler said the youth plaintiffs had sought to use the law to block development.
“In the Held v Montana case, they tried to twist MEPA into something it was never meant to be — a tool to deny permits and block development,” he said. “House Bill 285 sets the record straight: MEPA procedural, it’s a way to gather facts, weigh impacts, and make informed decisions — not dictate them.”
House Bill 291 specifies that Montana cannot adopt air quality standards stricter than federal rules, except in limited circumstances. Senate Bill 221 defines which impacts must be included in MEPA assessments and directs the DEQ to develop guidance for state agencies.
The youth plaintiffs say the new laws effectively reinstate restrictions already found unconstitutional.
“The Montana Supreme Court has already affirmed that we have a constitutional right to a clean and healthful environment, including a stable climate system, and the facts show we are being harmed right now,” lead petitioner Rikki Held said in a statement. “Yet the state just passed new laws that make these harms worse.”