MIKE PESCA, host:

This is DAY TO DAY from NPR News. I'm Mike Pesca.

MADELEINE BRAND, host:

And I'm Madeleine Brand.

Global warming was on the docket today at the Supreme Court. The justices heard arguments over whether the federal government can regulate carbon dioxide as an air pollutant.

Dahlia Lithwick is legal analyst for the online magazine Slate and a regular contributor to us here at DAY TO DAY, and she was at the court this morning. She joins us now. Hi Dahlia.

DAHLIA LITHWICK: Hi.

BRAND: Well, explain to us the science of global warming and why it was before the Supreme Court today.

LITHWICK: Well, I'm not going to attempt, Madeleine to explain the science. But I will tell you that this is a case in which the EPA, the Environmental Protection Agency, under President Bush, made the decision that they also wouldn't try to explain the science. They would not regulate the carbon emissions associated with cars - those emissions that are said to cause -create - greenhouse gases, which in turn are said to cause global warming.

Making that decision, tweaked a lot of states. And so 12 states, several cities, and some environmental and health groups all essentially brought suits, saying, you need to rethink this policy and start regulating those emissions. The EPA has claimed, and claimed again today, they don't the authority to regulate those emissions, because this is not classically-defined air pollution under the Clean Air Act.

And they go further and said: even if we did have the authority to regulate, we wouldn't because the scientific link between the two is unclear, and moreover it would be a bad thing for the U.S. to do so unilaterally. If I had to sum up the argument in a sentence it would be: I can't and I won't.

BRAND: And what happened in the lower courts before this got all the way up to the Supreme Court?

LITHWICK: The D.C. Circuit Court of Appeals struggled with this question. They, of course - three judges split three different ways on it - although they eventually sided with the EPA. One of the judges said yes, the EPA has the authority, they properly declined to regulate this.

Another judge said no, actually, the states that brought suit don't even have standing - legal standing - to sue, to be in court. And the third judge dissented and said of course the EPA should be regulating this and doing so right quick. And so the court granted cert to sort it all out.

BRAND: OK. And some dozen states and 13 environmental groups argued the opposite. What did they say this morning?

LITHWICK: Well first they had to get over this standing problem, and it is a huge problem. And the question is, whether there is, in fact, actual tangible harm that they can show. And the assistant attorney general from the state of Massachusetts, who argued this case, said, of course there's actual harm, look at our coastline.

The other thing they had to prove is that if the EPA went ahead and regulated these emissions it would, in fact, remedy the global warming problem. And again, I think that they took the position that it doesn't have to remedy all global warming, or even most global warming, it would be enough if we just did something at the EPA, and regulated some global warming.

And so they essentially just took the position that we don't need to stand here and show a direct numerical link between how much carbon emission we regulate in cars, and how much we can improve the global warming situation. We just have to say: something needs to be done and the EPA needs to do it.

BRAND: And the government again, said no, we can't and we won't?

LITHWICK: Pretty much, Madeleine. They again took this position that look these groups don't have any standing. They cannot show - Massachusetts cannot show that the failure to regulate cars has somehow caused global warming. And moreover, they cannot show that this tiny, tiny drop in the bucket - that you say in regulation, would, in fact, cure global warming. So they said, again, we can't and we won't.

BRAND: And could you tell which way the justices were leaning?

LITHWICK: Well, you're tired of hearing Madeline. I'm tired of saying it. It looked like another one of those four-four with Kennedy deciding days. And Kennedy did not speak too much - Anthony Kennedy.

So it's really hard to tell. It looked as though, certainly, that the more liberal justices were of the mind that you must and you must. If I could say anything I would say it was an impassioned day from the more liberal justices -about saving the environment.

BRAND: Dahlia Lithwick, legal analyst for the online magazine Slate, and for us here at DAY TO DAY. Thank you.

LITHWICK: My pleasure Madeleine. Transcript provided by NPR, Copyright NPR.