The North American Free Trade Agreement (NAFTA) is an international trade agreement among the United States, Canada, and Mexico that became effective on January 1, 1994. Pursuant to NAFTA most tariffs among the three countries are being phased out over a period of fifteen years. In addition, the agreement liberalizes rules regulating investment by United States and Canadian firms in Mexico. NAFTA includes side agreements on environment, labor, and dealing with import surges. Controversy surrounding the adoption of NAFTA by the United States in 1993 included issues related to trade, employment, immigration, labor law, and environmental protection. And, several years after its effective date, observers continue to debate the wisdom of the agreement. The economic slowdown in the United States that began in 2001 has intensified public debate over NAFTA's provisions.

While NAFTA's adoption was being debated, environmentalists were divided in response to whether...