The Supreme Court today considered the scope of the Environmental Protection Agency’s power to regulate greenhouse gases. According to early reports from oral arguments—and to the surprise of no one—the more liberal justices seemed open to allowing the EPA to regulate, while at least some of the more conservative justices were skeptical of allowing the EPA to venture further down this road. Justice Scalia, as per usual, made no effort to hide his views. He came out swinging against the EPA’s authority.

Justice Scalia was similarly outspoken seven years ago in oral arguments in the case that set in motion the EPA’s regulation of greenhouse gases. In Massachusetts v. EPA, the specific issue was motor vehicle emissions (whereas today’s arguments dealt with industrial plant emissions), but the underlying question about whether the Clean Air Act applies to greenhouse gases was the same. Justice Scalia believed then, and apparently still believes today, that the Clean Air Act’s provisions regarding “air pollution” should be read to apply to the air we breathe, but not to the pollution of the stuff beyond that, up in the sky, whatever it’s called. In the following exchange from the 2007 case, we get the rare instance of a brave lawyer correcting a justice in oral argument.

Justice Scalia: Mr. Milkey, I had… my problem is precisely on the impermissible grounds. To be sure, carbon dioxide is a pollutant, and it can be an air pollutant.

If we fill this room with carbon dioxide, it could be an air pollutant that endangers health.
But I always thought an air pollutant was something different from a stratospheric pollutant, and your claim here is not that the pollution of what we normally call “air” is endangering health.
That isn’t, that isn’t… your assertion is that after the pollutant leaves the air and goes up into the stratosphere it is contributing to global warming.

Mr. Milkey: Respectfully, Your Honor, it is not the stratosphere. It’s the troposphere.

Justice Scalia: Troposphere, whatever.
I told you before I’m not a scientist.
[Laughter]

That’s why I don’t want to have to deal with global warming, to tell you the truth.

Mr. Milkey: Under the express words of the statute… and this is 302(g)… for something to be an air pollutant it has to be emitted into the ambient air or otherwise entered there.

Justice Scalia: Yes, and I agree with that.
It is when it comes out an air pollutant.
But is it an air pollutant that endangers health?
I think it has to endanger health by reason of polluting the air, and this does not endanger health by reason of polluting the air at all.

Mr. Milkey: Your Honor, respectfully, I disagree, and there is nothing in the act that actually requires the harm to occur in the ambient air.
In fact, some of the harm here does occur there.

Justice Scalia: Well, it talks about air pollution all the time.
That’s what the, that’s what the thing is about, air pollution.
It’s not about global warming and it’s not about the troposphere.

Mr. Milkey: Your Honor, we are not saying, first of all that global warming is air pollution, any more than we’re saying that asthma is air pollution.
They’re both effects.
I would point you to the example of acid rain, where the pollutant there, sulfur dioxide, the problem is it causes its harm after it leaves the air, after it gets washed out.
Air pollutants do not need to cause harm in the ambient air.
Your Honor, I would add that our interpretation satisfies common sense because, while EPA has plenary authority over substances that motor vehicles emit, those substances are regulated only if EPA determines that they cause endangerment.
By defining the term “air pollutant” comprehensively, Congress has not prejudged what may cause endangerment, but it has allowed other pollutants to be regulated as their harms become appreciated.

Justice Scalia ultimately was outvoted on this one. He wrote a dissent explaining his narrow reading of the EPA’s statutory authority to air pollution. We await to see whether in this newest challenge to the EPA’s authority he is still in the minority.