The United States’ Marine Mammal Protection Act (MMPA) required U.S. boats to employ measures that would reduce the incidental taking of dolphins while fishing for tuna, or else be barred from selling in the U.S. market. Congress later supplemented the MMPA with the requirement that foreign countries implement comparable regulations as a condition of being able to import tuna into the U.S. market. The United States (defendant) subsequently imposed a tuna embargo against various countries, including Mexico (plaintiff). Mexico challenged the embargo before a General Agreement on Tariffs and Trade (GATT) panel. GATT Article XI forbids quotas, while Article III forbids discrimination in the importation of products from GATT parties. GATT Article XX(b) includes an exception to GATT limitations for measures implemented by a party that are necessary to preserve human, animal, or plant life. Mexico argued that the U.S. embargo violated Article XI’s quota prohibitions. The United States contended that the MMPA’s application and the imposed embargos were not quotas, but instead fit within and complied with Article III product guidelines. The United States argued, alternatively, that notwithstanding potential violations, the measures fell within the Article XX(b) exception. Mexico responded that Article XX(b) was inapplicable to any protective measures that reached outside the implementing party’s jurisdiction.