A treaty or convention is considered of equal standing to a statute. Thus when Congress ratified the North American Free Trade Agreement (NAFTA), any judicial decisions or previous statutes that were inconsistent—such as quotas or limitations on imports from Mexico that were opposite to NAFTA commitments—would no longer be valid. Similarly, US treaty obligations under the General Agreement on Tariffs and Trade (GATT) and obligations made later through the World Trade Organization (WTO) would override previous federal or state statutes.
One example of treaty obligations overriding, or taking priority over, federal statutes was the tuna-dolphin dispute between the United States and Mexico. The Marine Mammal Protection Act amendments in 1988 spelled out certain protections for dolphins in the Eastern Tropical Pacific, and the United States began refusing to allow the importation of tuna that were caught using “dolphin-unfriendly” methods (such as purse seining). This was challenged at a GATT dispute panel in Switzerland, and the United States lost. The discussion continued at the WTO under its dispute resolution process. In short, US environmental statutes can be ruled contrary to US treaty obligations.
Under most treaties, the United States can withdraw, or take back, any voluntary limitation on its sovereignty; participation in treaties is entirely elective. That is, the United States may “unbind” itself whenever it chooses. But for practical purposes, some limitations on sovereignty may be good for the nation. The argument goes something like this: if free trade in general helps the United States, then it makes some sense to be part of a system that promotes free trade; and despite some temporary setbacks, the WTO decision process will (it is hoped) provide far more benefits than losses in the long run. This argument invokes utilitarian theory (that the best policy does the greatest good overall for society) and David Ricardo’s theory of comparative advantage.
Ultimately, whether the United States remains a supporter of free trade and continues to participate as a leader in the WTO will depend upon citizens electing leaders who support the process. Had Ross Perot been elected in 1992, for example, NAFTA would have been politically (and legally) dead during his term of office.