Second, NAFTA eliminated many tariffs on imports and exports between the three countries. Tariffs are taxes that are used to increase the cost of foreign goods. NAFTA has developed specific rules to regulate trade in agricultural products, motor vehicles and clothing. Many critics of NAFTA saw the agreement as a radical experiment developed by influential multinationals who wanted to increase their profits at the expense of ordinary citizens of the countries concerned. Opposition groups argued that the horizontal rules imposed by nafta could undermine local governments by preventing them from enacting laws or regulations to protect the public interest. Critics also argued that the treaty would lead to a significant deterioration in environmental and health standards, promote privatization and deregulation of essential public services, and supplant family farmers in the signatory countries. See z.B. Gary Clyde Hufbauer and Jeffrey J. Schott, NAFTA Revisited: Achievements and Challenges, Institute for International Economics, October 2005; Center for Strategic and International Studies, NAFTA`s Impact on North America: The First Decade, Edited by Sidney Weintraub, 2004; and U.S. Chamber of Commerce, Opening Markets, Creating Jobs: Estimated U.S.
Employment Effects of Trade with FTA Partners, 2010. According to the Sierra Club, NAFTA has contributed to large-scale export-oriented agriculture, resulting in increased use of fossil fuels, pesticides and GMOs.  NAFTA has also contributed to environmentally harmful mining practices in Mexico.  It has prevented Canada from effectively regulating its oil sands industry and has created new legal opportunities for transnational companies to combat environmental legislation.  In some cases, environmental policy has been neglected as a result of trade liberalization; In other cases, NAFTA`s investment protection measures, such as Chapter 11, and measures to address non-tariff barriers to trade have threatened to discourage stronger environmental policy.  The most severe increases in pollution attributable to NAFTA were in the base metals, Mexican petroleum and transportation equipment sectors in the United States and Mexico, but not in Canada.  Clinton signed it on December 8, 1993. The agreement came into force on 1 January 1994.
  At the signing ceremony, Clinton paid tribute to four people for their efforts to reach the historic trade agreement: Vice President Al Gore, Council of Economic Advisers Chair Laura Tyson, National Economic Council Director Robert Rubin and Republican Congressman David Dreier.  Clinton also said, “NAFTA means jobs. U.S. jobs and well-paying American jobs.