Gorsuch and the other justices wrestled with the concept of "ambiguity," a key factor in whether Chevron deference applies.
If Congress delegates authority to a regulatory agency to decide an issue and the court determines the law is clear with respect to this issue, then the court must implement congressional intent.
However, if a court determines a law is silent or ambiguous on an issue before the court, then the court should defer to the agency if the court decides the interpretation of the law is reasonable.
"You need a secret decoder ring" to define it, said Martinez, the lawyer for the Relentless Inc. petitioners.
Since Chevron deference was born, "some judges claim never to have found an ambiguity and other equally excellent circuit judges have said they find them all the time," Gorsuch said.
"And it's also why, I don't know, maybe a dozen or more circuit judges have written asking us to overrule Chevron," he added. "So many lower court judges who just want to follow whatever we tell them to do faithfully can't figure it out."
In saying regulators are better-suited than judges to address a law's ambiguity, Kagan offered an analogy of Congress passing an artificial intelligence law.
"Just by the nature of things and especially the nature of the subject, there are going to be all kinds of places where, although there's not an explicit delegation, Congress has, in effect, left a gap," she said.
"It has created an ambiguity. And what Congress is thinking is, do we want courts to fill that gap, or do we want an agency to fill that gap?" she added.
"Congress knows that there are going to be things that it writes that it's just not going to be clear how this will apply or what it will mean with respect to countless factual situations that this country will have to address," she said. "Does the Congress want this court to decide those questions, policy-laden questions, of artificial intelligence?"
Chief Justice Roberts asked Martinez how the Supreme Court should address Chevron deference because the court hasn't reviewed this doctrine since 2016. "I just wonder how often this comes up?"
Even though the Supreme Court hadn't recently reviewed it, "the lower courts still have to apply it," Martinez said.
Roberts directed the same question to Prolegar. By not reviewing the doctrine for so long, "have we overruled it in practice even if we've had to leave the lower courts to continue to grapple with it?"
Just because the court hasn't made a ruling on the Chevron doctrine's second-step process relating to ambiguity, Prolegar said, that "in no way indicates that in those cases where Congress is, in fact, leaving ambiguities or gaps, Chevron no longer sets the right ground rule for understanding the scope of the delegation" of responsibility.