In an 8–1 majority decision, the Court determined that Chevron deference applies when Congress delegated authority to the agency generally to make rules carrying the force of law.

The Mead Corporation challenged a ruling of the United States Customs Service that classified its day planners as "diaries, notebooks and address books, bound," which were subject to a tariff.

Before Mead, it was clear that the Chevron doctrine applied to interpretations adopted in legislative rules and certain formal adjudications, but lower courts differed on whether it also applied to interpretative rules, policy statements, informal adjudications, advisory letters, and amicus briefs.

In 2001, the Supreme Court finally began to shed some light on the issue.

Justice Souter wrote that "administrative implementation of a particular statutory provision qualifies for Chevron deference when it appears that Congress delegated authority to the agency generally to make rules carrying the force of law, and that the agency interpretation claiming deference was promulgated in the exercise of that authority.