Throughout the past decade, the United States Supreme Court has questioned the constitutionality of affording deference to a federal agency’s interpretation of its own regulations. This level of deference originated with the Court’s 1945 opinion in Bowles v. Seminole Rock & Sand Co., and in 1997, the Court reinvigorated Seminole Rock in Auer v. Robbins. The impact of “Auer deference” has continued to grow with the expansion of the administrative state. But the intersection of a Supreme Court in flux with a presidential administration that has proposed major new environmental regulations may yet pose an opportunity for the Court to revisit this fundamental doctrine in administrative law.