In late 2019, the Trump administration gained the support of congressional Democrats for the USMCA after agreeing to incorporate stricter enforcement of labor laws. In the updated pact, the parties agreed on a number of changes: the rules of origin for the automotive industry were strengthened, so that 75% of each vehicle must come from member countries, compared to 62.5%; and new labor regulations have been added that require 40% of each vehicle to come from factories that pay at least $16 an hour. A proposal to expand intellectual property protection for U.S. pharmaceuticals — a long red line for U.S. trade negotiators — has been sacrificed. The USMCA also significantly reduces the controversial investor-state dispute settlement mechanism, eliminating it entirely with Canada and limiting it to certain sectors with Mexico, including oil and gas and telecommunications. After diplomatic negotiations in 1990, the leaders of the three nations signed the agreement on December 17, 1992 in their respective capitals.  The signed agreement then had to be ratified by the legislature or parliament of each country. The Clinton administration negotiated a subsidiary environmental agreement with Canada and Mexico, the North American Agreement on Environmental Cooperation (NAAEC), which led to the creation of the Commission for Environmental Cooperation (CEC) in 1994. To address concerns that NAFTA, the first regional trade agreement between a developing and two developed countries, would have a negative impact on the environment, the Commission was mandated to carry out an ongoing ex-post environmental assessment. It created one of the first ex-post frameworks for the environmental assessment of trade liberalization, which aimed to provide a body of evidence regarding the initial assumptions about NAFTA and the environment.
such as concerns that NAFTA would create a „race to the bottom“ in environmental regulation between the three countries, or that NAFTA would pressure governments to increase their environmental protection.  The CEC held four symposia to assess the environmental impact of NAFTA and commissioned 47 papers on the subject from leading independent experts.  United States. . . .