HELENA, Mont. — Montana’s Supreme Court on Wednesday upheld a landmark climate ruling that said the state was violating residents’ constitutional right to a clean environment by permitting oil, gas and coal projects without regard for global warming.

The justices, in a 6-1 ruling, upheld an August 2023 decision by a state judge that was considered a breakthrough in attempts by young environmentalists and their attorneys to use the courts to leverage action on climate change.

The justices found a policy that prevented Montana from considering the effect of greenhouse gases when issuing permits for fossil fuel development is unconstitutional.

The state had appealed the ruling and the arguments were held before the Montana Supreme Court in July.