GEOFF BENNETT: For those of you just rejoining us, we have been exploring the landmark court case in Montana, where young climate activists challenged the state's promotion of fossil fuels, and won.

William Brangham, is here now to explain yesterday's ruling and help us understand the broader implications in Montana and nationwide.

William, it's always great to see you.

WILLIAM BRANGHAM: Nice to see you.

GEOFF BENNETT: So, for folks who didn't get to see your earlier report, remind us of the argument these young people in Montana were making, this argument that was just affirmed in court yesterday.

WILLIAM BRANGHAM: These young people were arguing that Montana's embrace of fossil fuels was hurting the state's environment by pumping all these carbon emissions into the air, and that that was harming the environment, that it was driving climate change, and that it was violating the state's Constitution, which Montana has this very unique clause in its Constitution, which says that citizens have a right to a clean and healthful environment.

And Judge Kathy Seeley agreed with them and said that, because the state was not looking at the carbon emissions of any fossil fuel project when it was going to issue permits, that it was violating the Constitution.

So, that was the judgment yesterday.

These students were represented by Our Children's Trust, which is an environmental law firm based out of Oregon.

And they have tried similar cases in other states.

None of them have been successful.

They have one federal case that has gotten forward, but it's stalled in the courts now.

So this is really the first of its kind in the country.

The state of Montana was represented by its attorney general.

They derided the case all along and implied that the kids were basically being used by this law firm.

And they have vowed to appeal the ruling.

GEOFF BENNETT: So, assuming this ruling survives the appeal, what might the impact be, not just in Montana, but across the country?

WILLIAM BRANGHAM: The impact in Montana is to be determined.

The ruling means that the state legislature, which, in Montana, is GOP-dominated and very friendly to the fossil fuel industry, they will determine how the state goes forward in assessing whether carbon emissions should deter or allow a fossil fuel project to go forward.

Montana makes a lot of coal, and it's a big industry, a lot of jobs, a lot of -- important part of the economy there.

So it may not be such a big impact in Montana immediately.

I talked today with a guy named Michael Burger.

He runs the Sabin Center for Climate Study at Columbia University.

And he argues that the longer impact, the broader impact of this ruling will be nationwide, because the findings of fact in this case were affirmed by the judge that said, climate change is real, that emissions drive climate change, that climate change can be harmful, and that local emissions in your own state can damage the people who live in that state.

He says those findings of fact are substantial and that it's not setting precedent around the country, but that a lot of other cases -- and there are a lot of other cases going on.

There are several other youth cases that are going.

There's a lot of litigation against fossil fuel industries.

These findings of facts could have a much broader impact and could ripple out nationwide.

GEOFF BENNETT: William Brangham, thanks so much for that reporting.

Appreciate it.

WILLIAM BRANGHAM: My pleasure, Geoff.

GEOFF BENNETT: And if you missed William's original report looking at the case of the young activists in Montana, you can find it at PBS.org/NewsHour.