Editors' Summary: On September 3, 1991, a three-member dispute resolution panel formed by the signatories to the General Agreements on Tariffs and Trade (GATT) held that a U.S. embargo on Mexican tuna and tuna products harvested in the Eastern Tropical Pacific Ocean violated GATT. The resulting controversy has focused on the decision's effect on U.S. actions under the Marine Mammal Protection Act (MMPA), and the ramifications to other U.S. environmental laws with international trade impacts. The authors describe the legal background of this decision, including the GATT and MMPA provisions addressed by the panel, analyze the decision in depth, and discuss the recent U.S. District Court for the Northern District of California decision enjoining the Secretaries of Commerce and the Treasury and the National Marine Fisheries Service from allowing intermediary nations to import tuna from embargoed harvesting nations into the United States. Finally, the authors analyze the potential effects of the panel's decision on domestic laws and international laws and agreements and conclude that although the decision's policy ramifications will be significant, it will have little effect on U.S. law.