In a nearly 30 year old Duke Law Journal article, Justice Scalia asked with regard to Chevron deference, “How clear is clear?” Last week in Mexichem Fluor, Inc. v. EPA, Judges Brett Kavanaugh and Robert Wilkins took opposing views on whether section 612 of the Clean Air Act is clear enough to stop at Chevron’s first step. That section provides in part that ozone-depleting substances “shall be replaced by chemicals, product substitutes, or alternative manufacturing processes that reduce overall risks to human health and the environment.”

Despite the EPA’s statements over the years that section 612 doesn’t give the agency authority to require the replacement of non-ozone-depleting substances, that’s just what the EPA did in 2015. After the EPA concluded that hydrofluorocarbons (HFCs) contribute to climate change (but don’t deplete the ozone layer), the agency promulgated a final rule that moved HFCs from the list of safe substitutes to prohibited substitutes.

In Judge Kavanaugh’s view (joined by Judge Janice Rogers Brown), the EPA couldn’t ban a company from using HFCs if the company had switched to using them when they were on the safe substitutes list. He reasoned that such an entity had already replaced its ozone-depleting substances with a substitute that didn’t deplete the ozone layer and that was then on the safe list. In other words, because HFCs don’t deplete the ozone layer, there’s no longer the regulatory predicate that would allow the EPA to prescribe a substitute—at that point, “there is no ozone-depleting substance to ‘replace.’” To conclude otherwise would clearly contravene the text of the statute, in the majority’s view.

Judge Wilkins didn’t find the text clear enough, though. In his view, the word “replace” is ambiguous because Congress could have intended replacement to be a process rather than specific instances. Thus, EPA could regulate substitutes under section 612 as long as ozone-depleting chemicals are in existence or in use for a particular industry or end use, even if the particular regulated entity no longer uses them.

While Judge Wilkins’s interpretation isn’t implausible, Judge Kavanaugh’s reading is surely the natural one. The split here would probably occur anyway, but Chevron clutters up interpretive disputes like these by obscuring them with arguments over the relative clarity or ambiguity rather than just getting down to business of determining the best interpretation. Hopefully the day is coming soon when the Supreme Court seriously rethinks this infamous doctrine.