Imports into the United States were taxed pursuant to the Harmonized Tariff Schedule of the United States (HTSUS). The United States Customs Service (Customs) set the final classifications and tariff rates under the HTSUS pursuant to rules and regulations promulgated by the United States Secretary of the Treasury. Tariff classifications for imports were made in "ruling letters" issued before entry of the goods. Ruling letters were not subject to notice and comment before being issued and could be modified without notice and comment in most circumstances. Instead, rulings were subject to independent review by the Court of International Trade (CIT). The Mead Corporation (Mead) (plaintiff) imported day planners. Between 1989 and 1993, Customs treated Mead's day planners as a duty-free import. However, in January 1993, Customs issued a ruling letter classifying the day planners as bound diaries subject to a 4 percent tariff under the HTSUS. Mead brought an action against the United States (defendant) in the CIT, which granted the government's motion for summary judgment and adopted Customs's reasoning as to why the planners were bound diaries and thus subject to the tariff. Mead appealed to the United States Court of Appeals for the Federal Circuit, which reversed the CIT. The appeals court gave no deference to the ruling letter and rejected Customs's reasoning that the day planners were either bound or diaries. The United States Supreme Court granted certiorari to consider the issue of how much deference courts owed to this type of agency action.