What qualifies as a “mine”? KC Transport, Inc.—a family-run trucking company—was blindsided when a federal agency declared that each of its trucks constituted a “mine” and therefore fell under onerous federal regulations. Relying on the now-defunct Chevron doctrine, a court of appeals upheld the agency’s interpretation as “permissible.” Because Chevron has since been overruled by the Supreme Court, that decision cannot stand.

The Cato Institute has now joined the Manhattan Institute to file an amicus brief in the D.C. Circuit in support of KC Transport. Our brief urges the court of appeals to heed the Supreme Court’s instructions and pay no deference to the government’s arbitrary definition of “mine.” Deference to the executive branch is inconsistent with the judiciary’s function as the primary expositor of statutes. Moreover, deferring in this case is particularly inappropriate given the government’s novel and counterintuitive definition of a “mine.”

Although Chevron’s regime of deference might have been created with good intentions, in practice it provided a license for inconsistent interpretations and executive overreach. For 40 years, courts struggled to distinguish incorrect-but-permissible interpretations from interpretations beyond the pale of deference. The result was a decades-long expansion of administrative power that infringed upon the legislative functions of Congress, the sovereignty of states, and individual liberty. The Supreme Court has now recognized and corrected these errors. Consequently, the D.C. Circuit must avoid reintroducing deference under another guise.

Courts need not ignore agency interpretations altogether, but must limit their weight to situations where those interpretations possess the “power to persuade.” Persuasive interpretations are generally longstanding, contemporaneous with the statute, and rooted in agency expertise. The government’s reading of “mine” meets none of these criteria. Indeed, the agency has repeatedly shifted its position during litigation to avoid unfavorable rulings. This inconsistency—and the lack of foundation for the latest agency pronouncement—shows that the government’s analysis deserves no special weight. The DC Circuit should rule against the agency’s implausible interpretation.