T he North American Free Trade Agreement (NAFTA) entered into force on January 1, 1994 ( P.L. 103-182 ), establishing a free trade area as part of a comprehensive economic and free trade agreement among the United States, Canada, and Mexico. Although some industries may have reduced their U.S. operations, in general, NAFTA is considered to have benefitted the United States economically as well as strategically in terms of North American relations. The U.S. food and agricultural sectors, which is the focus of this report, has benefitting especially from NAFTA. The U.S. Department of Agriculture (USDA) and many agricultural industry groups claim that NAFTA has positively affected U.S. agricultural markets. NAFTA continues to be of interest to Congress given continued strong trilateral trade and investment ties and the agreement's significance for U.S. trade policy. President Trump has repeatedly stated that he intends to either renegotiate or withdraw from NAFTA. In May 2017, the U.S. Trade Representative (USTR) notified Congress of the Administration's intent to renegotiate NAFTA. USTR is scheduled to conduct a public hearing in late June 2017 and also requested public comment on "matters relevant to the modernization" of NAFTA. In response to congressional concerns that NAFTA's renegotiation could be "unsettling" to the U.S. agricultural community, the Administration has assured Congress that it will "do no harm" to existing U.S. agricultural export markets and will prioritize U.S. agricultural exports in the renegotiation. It is significant that all three NAFTA countries participated in the Trans-Pacific Partnership (TPP) agreement from which the United States withdrew in January 2017, because TPP represented the most recent attempt to design a modern regional free trade agreement (FTA). For more background information on NAFTA and the current status of the Administration's activities, see CRS Report R42965, The North American Free Trade Agreement (NAFTA) , and CRS In Focus IF10047, North American Free Trade Agreement (NAFTA) . NAFTA's primary objectives were "to eliminate barriers to trade in, and facilitate the cross-border movement of goods and services" among the NAFTA countries. NAFTA's market access provisions were structured as three separate bilateral agreements. The first agreement, the Canada-United States Trade Agreement (CUSTA), took effect on January 1, 1989, and was later subsumed into NAFTA and included certain additional provisions. The second and third agreements are both under NAFTA—one between Mexico and the United States and another between Canada and Mexico. These latter agreements took effect on January 1, 1994. For agriculture, NAFTA (including CUSTA) eliminated tariffs and addressed other types of non-tariff barriers to trade, such as quotas, licenses, and other types of restrictions and standards. NAFTA's agricultural provisions are contained within the "Agriculture and Sanitary and Phytosanitary Measures" chapter (Chapter 7), but provisions in other chapters also apply. The text box provides a summary of NAFTA's provisions that address agricultural trade. For agriculture, certain restrictions on bilateral trade were eliminated immediately upon implementation, while other restrictions were phased out over either a period of 4-, 9-, or 14-years ( Table 1 ). Sensitive products, such as sugar, were given the longest phase-out period. Tariff elimination for agricultural products under CUSTA concluded on January 1, 1998. However, quotas for certain agricultural products in U.S.-Canada trade were not liberalized. This was carried over without change into NAFTA. In the World Trade Organization (WTO) Uruguay Round, all import quotas were converted to tariff-rate quotas (TRQs). Accordingly, within-quota trade occurs at the duty-free tariff treatment agreed to in CUSTA, but the over-quota trade occurs at the WTO bound tariff equivalent of the old quota, which is not liberalized. Under CUSTA, Canada excluded dairy, poultry, and eggs for tariff elimination. In return, the United States excluded dairy, sugar, cotton, tobacco, peanuts, and peanut butter. Because Canada was able to exclude dairy products, poultry, and poultry products (including eggs) from tariff elimination in NAFTA, Canada is able to maintain a supply management system for these sectors by limiting imports through restrictive TRQs. These products were also exempt from Canada-Mexico trade liberalization. Tariff elimination for agricultural products under NAFTA concluded on January 1, 2008. Most non-tariff trade barriers in U.S.-Mexico agricultural trade were converted to either tariffs or TRQs. Prior to NAFTA, Mexico's trade-weighted tariff on U.S. products averaged about 11%. Tariffs for some agricultural products were higher, such as Mexican tariffs for fruits and vegetables, which averaged about 20% before NAFTA. Also prior to NAFTA, certain agricultural products—wheat, tobacco, cheese, evaporated milk, grapes, corn, dry beans, poultry, barley/malt, animal fats, potatoes and eggs—were subject to Mexican import licensing requirements affecting a reported 25% of the value of U.S. agricultural exports. Mexico also applied certain "official import prices," an arbitrary customs valuation system that raised duty assessments. In the United States, import quality requirements administered by USDA have affected imports of some Mexican products such as tomatoes, onions, avocados, grapefruit, oranges, olives, and table grapes. U.S. agricultural imports subject to reduced TRQ under NAFTA include sugar, beef, dairy products, peanut butter and paste, cotton, apparel, and cotton (from Canada) and beef, apparel, fabric, and yarn (from Mexico). In addition to tariffs and quotas, NAFTA addressed SPS measures and other types of non-tariff barriers that may limit agricultural trade. NAFTA requires that SPS measures be scientifically based, nondiscriminatory, and transparent and minimally affect trade. SPS measures are laws, regulations, standards, and procedures that governments employ as "necessary to protect human, animal or plant life or health" from the risks associated with the spread of pests, diseases, or disease-carrying and causing organisms or from additives, toxins, or contaminants in food, beverages, or feedstuffs. For agricultural exporters, SPS regulations are often regarded as one of the greatest challenges in trade, often resulting in increased costs and product loss and also the potential to disrupt integrated supply chains. A related issue involves technical barriers to trade (TBT). TBTs cover both food and non-food traded products. TBTs in agriculture include SPS measures and other types of measures related to health and quality standards, testing, registration, certification requirements, and packaging and labeling regulations. For more background information, see text box . Although NAFTA entered into force before the WTO was established and the WTO's Agreement on Sanitary and Phytosanitary Measures ("SPS Agreement") was implemented, it contains a detailed SPS chapter and imposes specific disciplines on the development, adoption, and enforcement of SPS measures. Some consider NAFTA's SPS provisions as establishing the blueprint for the SPS Agreement. Similar to the SPS Agreement, NAFTA's SPS disciplines are designed to prevent the use of SPS measures as disguised trade restrictions. SPS measures should also be scientifically based and consistent with international and regional standards while at the same time explicitly recognizing each country's right to determine its appropriate level of protection (e.g., to protect consumers from unsafe products or to protect domestic crops and livestock from the introduction of foreign pests and diseases). NAFTA also established a Committee on Sanitary and Phytosanitary Measures to facilitate technical cooperation in the development, application, and enforcement involving SPS measures. The committee meets periodically to review and resolve SPS issues and also hosts a number of technical working groups to enhance regulatory cooperation and facilitate trade between the NAFTA countries. Working groups address, for example, national regulatory and scientific review capacity, as well as coordination and harmonization of pesticide standards among the NAFTA partner countries. USTR regularly reports on a range of ongoing trade concerns in its annual National Trade Estimate Report on Foreign Trade Barriers (NTE) report, which covers trade barriers affecting U.S. agricultural and non-food exports for the major U.S. trading partners. The most recent NTE report highlights certain outstanding issues involving SPS and U.S. trade with its NAFTA partners. Select trade disputes between the United States and its NAFTA partners are discussed later in " Addressing Outstanding Trade Disputes ." NAFTA created both formal and informal mechanisms to resolve trade disputes among partner countries. NAFTA's formal mechanism for resolving disputes covers the agreement's provisions for investment (Chapter 11) and services (Chapter 14), the antidumping (AD) and countervailing duty (CVD) determinations (Chapter 19), and the general interpretation and application of the agreement (Chapter 20). NAFTA's rules-based systems for resolving disputes is meant to strengthen trade relations by providing an orderly, legal framework that defines and protects the interests of all partner countries. Table 2 highlights selected examples of dispute resolution through NAFTA, encompassing AD and CVD actions, NAFTA arbitration panels, government and industry negotiations, and technical assistance involving SPS measures. Agricultural AD and CVD investigations and duty assessments under Chapter 19 provide a way for NAFTA countries to address trade disputes resulting from perceived unfair trade practices. It allows exporters and domestic producers a way to make their case and appeal the results of trade-remedy investigations before an independent and objective binational panel, and it provides an alternative option to judicial review of such decisions before domestic courts.