The United States maintained that the import restriction on tuna was justified under the GATT's national treatment provision. The United States also argued that the prohibition was valid under Article XX of the GATT, which provides for exceptions for animal health or exhaustible natural resources. The GATT panel also found that Article XX does not allow trade restrictions to enforce a country's own laws outside its jurisdiction. Thus, Mexico's position was upheld on both counts. The panel, however, found the U.S. Dolphin Protection Consumer Information Act to be GATT consistent.
Economists generally oppose import restrictions to enforce PPMs for two main reasons.
First, PPMs represent one of many types of differences among economies that are the basis for trade. If such differences are eliminated, some or all of the expected economic gains from specialization could be lost. Second, the use of trade restrictions for environmental PPMs could quickly lead to a proliferation of trade restrictions due to differences in other kinds of policies. Moreover, some economists argue that unilateral trade restrictions, such as that imposed in the tuna-dolphin case, violate the sovereignty of other nations. Countries may evaluate the costs and benefits of environmental measures differently.