I wrote a post every week about the D.C. Circuit from August 2015 to August 2020.* Then I stopped. Life is busy.

But I still read the D.C. Circuit’s opinions. And today seems like a good day for a quick post. After all, today’s opinion is all about deference — which is what I’ve been thinking a lot about lately.*

The case is Sierra Club v. EPA (again). It concerns National Ambient Air Quality Standards. And Judge Tatel, joined by Judges Katsas and Edwards, offers a full helping of Chevron. Indeed, the Court’s opinion has four sections of analysis, and each is a springboard for discussion.

First, consider this language: “the ratio of total emission reductions of volatile organic compounds to total increased emissions of such air pollutant shall be ….” Is it ambiguous about what “air pollutant” means? No, says the Court:

Second, are the terms “baseline emissions” and “milestones” ambiguous? Yes, says the Court, but EPA still loses at Chevron Step 2:

Third, what about “baseline” by itself?

And fourth, what about the language “measures shall be included in the plan revision as contingency measures to take effect in any such case”? Unambiguous, says the Court:

As you can tell, this is a complicated case. Each section of the opinion contains a lot more explanation; if you study environmental law, you should read the full opinion. But for everyone, it is interesting to see so many different types of Chevron questions in one place.

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* Next Friday, the Duke Law Journal is hosting a virtual symposium on Chevron (registration is free). Kristin Hickman and I wrote the foreword and will be presenting our proposal for Chevron reform.

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