The U.S. Supreme Court's Chevron, U.S.A., Inc. v Natural Resources Defense Council, Inc.¹ decision has dominated administrative case law and scholarship for nearly 20 years.² In 1999, this dominance prompted the participants in the bi-annual Administrative Law Discussion Forum to plead that the next Forum topic be "anything other than Chevron!"³ At the 2001 Forum, however, Chevron again took center stage,⁴ driven to the fore by the Court's then-recent decisions in Christensen v. Harris County⁵ and United States v. Mead Corp.⁶

One would think that after all this time and discussion we would know what Chevron means. Far from it. In 2001, Thomas Merrill's and Kristin Hickman's influential article, Chevron's Domain,⁷ identified 14 unanswered questions concerning the application of Chevron deference to agency statutory interpretation. Mead represented an opportunity to provide clear answers to at least one of these questions, and perhaps two others.⁸ Unfortunately, as discussed below, Mead only confirmed the uncertainty as to when Chevron deference is available to agency statutory interpretations.