Montana’s Supreme Court on Wednesday upheld a 2023 ruling siding with young climate activists who asserted the state government violated their right to a healthy environment.

In August 2023, Montana’s First Judicial District sided with the 16 plaintiffs, who cited a state constitutional provision guaranteeing “a clean and healthful environment” to argue the state violated that right with a law that barred weighing climate impacts during the approval process for energy projects.

The state supreme court upheld the finding in a 6-1 ruling Wednesday, writing, “Montana’s right to a clean and healthful environment and environmental life support system includes a stable climate system, which is clearly within the object and true principles of the Framers inclusion of the right to a clean and healthful environment.” Justice Jim Rice, who was appointed by former Gov. Judy Martz (R), was the only dissent.

The court rejected an argument from Montana Attorney General Austin Knudsen (R) that state-level efforts will have no effect without action from the rest of the world, comparing that argument to “the old ad populum fallacy: ‘If everyone else jumped off a bridge, would you do it too?’”

The plaintiffs’ attorney, Melissa Hornbein of the Western Environmental Law Center, hailed the decision as “a monumental moment” for young people and the state.

“This ruling clarifies that the Constitution sets a clear directive for Montana to reduce its greenhouse gas emissions, which are among the highest in the nation on a per capita basis, and to transition to a clean, renewable energy future,” she said.

Knudsen’s office criticized the decision in a statement, with Montana Justice Department Press Secretary Chase Scheuer calling the ruling “disappointing, but not surprising.”

“The majority of the state Supreme Court justices yet again ruled in favor of their ideologically aligned allies and ignored the fact that Montana has no power to impact the climate,” Scheuer said.

Montana Supreme Court justices are directly elected to eight-year terms but midterm replacements are appointed by the governor. Two of Montana’s governor-appointed judges were named by Gov. Steve Bullock (D), while Rice is the only justice appointed by a Republican.