Van Gend en Loos (plaintiff) imported urea-formaldehyde from West Germany into the Netherlands in September 1960. Under a tariff reclassification effective March 1, 1960, urea-formaldehyde was subject to an 8 percent tariff. Van Gend en Loos challenged the 8 percent tariff in a Dutch court, arguing that, as of January 1, 1958, the urea-formaldehyde was subject to a 3 percent tariff under the European Economic Community Treaty (EEC Treaty). Van Gend en Loos argued that the tariff reclassification violated Article 12 of the EEC Treaty, as the Dutch tariff was higher than the tariff under the EEC. Article 12 of the EEC Treaty prohibited signatories from raising existing tariff percentages for goods already traded between member states. The Dutch customs collectors, Nederlandse Administratie der Belastingen (defendant), argued that the product had a 10 percent duty based on its classification on January 1, 1958, so the 8 percent tariff was not an increase prohibited by Article 12. Before considering the appropriate tariff percentage, the Dutch court hearing the case, the Tariefcommissie, requested that the European Court of Justice (ECJ) render a preliminary judgment on the claim under Article 12 of the EEC Treaty in a Dutch court.