The World Trade Organization's (WTO) Agreement on Technical Barriers to Trade (TBT Agreement) establishes obligations that WTO members must adhere to when they impose requirements on a product's characteristics. To date, relatively few WTO disputes have been raised challenging member compliance with the TBT Agreement's provisions. However, in recent years, the United States has faced claims alleging its failure to abide by the terms of the TBT Agreement. In two of these cases, which are still ongoing, the WTO found that certain U.S. labeling requirements for food products violated the TBT Agreement's nondiscrimination obligations—that is, the measures at issue treated foreign products less favorably than domestic products. The Appellate Body reports from these two disputes provide insight into how the WTO applies these nondiscrimination provisions, and can provide guidance for Congress to consider when enacting future programs that regulate product characteristics. This report analyzes the Appellate Body decisions in two disputes: U.S. – Certain Country of Origin Labeling Requirements ( U.S. – COOL ) and U.S. – Measures Concerning the Importation, Marketing and Sale of Tuna and Tuna Products ( U.S. – Tuna II ). In 2008, Canada and Mexico, through WTO dispute settlement procedures, requested consultations with the United States regarding U.S. country of origin labeling (COOL) requirements for certain beef and pork products. In the WTO dispute U.S. – COOL , Canada and Mexico claimed that the labeling program, inter alia , violated U.S. obligations under the TBT Agreement, arguing that the COOL program impermissibly treated foreign livestock less favorably than domestic livestock. After the parties exhausted the available dispute settlement procedures, including appeals, the WTO Appellate Body ruled in favor of Canada and Mexico, finding that the COOL program impermissibly discriminated against the foreign livestock. After the WTO reached its final decision on the merits in May 2015, Canada and Mexico requested permission from the WTO to retaliate against the United States through the suspension of concessions. The WTO Dispute Settlement Understanding (DSU) allows WTO members to retaliate against an offending party by raising tariffs or suspending other concessions made under WTO agreements in an amount equal to the impairment of trade caused by the offending measure. In their request for retaliation, Canada and Mexico have claimed that the U.S. COOL program, as currently implemented, impairs trade by approximately $3 billion per year. The United States has challenged the amounts that Canada and Mexico have claimed—that appeal is currently being heard by arbitrators at the WTO, with a decision on the amount of impairment due in the coming months. In another recent WTO case involving the United States, U.S. – Tuna II , Mexico claimed that the United States' "dolphin-safe" labeling program for tuna products, established by the Dolphin Protection Consumer Information Act (DPCIA), also violated the TBT Agreement. In that case, Mexico argued that the dolphin-safe label program impermissibly treated tuna from Mexico less favorably than domestic tuna and tuna from other foreign nations. To date, the WTO has ruled in favor of Mexico in this dispute as well; however, Mexico and the United States are awaiting a decision from the WTO's Appellate Body. If Mexico succeeds on appeal, it would be able to seek permission from the WTO to retaliate against the United States. These disputes were two of the first Appellate Body rulings to apply the nondiscrimination requirements of the TBT Agreement. The United States lost both of these disputes for failing to comply with those obligations established in Article 2.1 of the TBT Agreement, the focus of this report. First, to provide a basic understanding of the objectives and requirements of the TBT Agreement, this report provides a general overview of that instrument. Next, it briefly describes the regulatory programs at issue in these two WTO disputes and analyzes how the WTO's Appellate Body applied Article 2.1 in U.S. – COOL and U.S. – Tuna II . The report takes an in-depth look at the test established by the Appellate Body for determining whether a measure is impermissibly discriminatory. Finally, the report provides a brief description of how the United States amended these programs in response to the WTO decisions, and explains why subsequent WTO rulings found that the amended programs still failed to comply with international trade obligations. Shortly following World War II, developed countries sought to reach a multilateral international agreement aimed at reducing barriers to international trade. In 1947, these countries established the General Agreement on Tariffs and Trade 1947 (GATT 1947) in order to reduce tariffs and implement rules preventing discrimination in international trade. Through this agreement, the international community sought to liberalize trade markets and provide for a greater flow of goods across international borders. However, in the decades following the establishment of the GATT 1947, countries sought to further open global markets by reducing non-tariff barriers to trade. The international community recognized that countries frequently adopt measures that regulate a product's characteristics, typically to protect the environment or human health, ensure the quality of products, prevent deceptive practices, or achieve some other legitimate objective. However, these measures can be trade-distorting, and sometimes countries implement such regulations solely to protect domestic markets. To that end, the TBT Agreement is intended to balance the need to protect members' regulatory autonomy with the need to prevent unnecessary obstacles to international trade. The WTO members announced that they were establishing the TBT Agreement to "ensure that technical regulations and standards, including packaging, marking and labelling requirements, and procedures for assessment of conformity with technical regulations and standards do not create unnecessary obstacles to international trade." The TBT Agreement furthers this goal by providing a set of legal obligations that WTO members must adhere to when establishing such measures. The TBT Agreement applies to measures that regulate a product's characteristics. A measure is covered under the TBT Agreement if it regulates on the basis of a product's intrinsic qualities, qualities that are related to the product, or qualities that the product lacks. Characteristics that are related to the product include their identification, presentation, and appearance. In EC – Sardines , for example, Peru challenged an EU regulation establishing standards for what qualified as preserved sardines. The EU regulation established that only one kind of fish, Sar d ina pilchardus , could be labeled for sale as "preserved sardines." The Appellate Body held that this measure prescribed product-related characteristics because it conditioned the labeling of a product based on specific product characteristics, the species of fish. Similarly, in EC – Asbestos , the Appellate Body found that a French decree criminalizing the sale of products containing asbestos fibers fell under the scope of the TBT Agreement because it required all products to have a shared characteristic—that is, all products had to be asbestos-free. The TBT Agreement classifies measures that regulate on the basis of a product's characteristics into three categories: (1) technical regulations; (2) standards; and (3) conformity assessment procedures (CAPs). Technical regulations are documents that prescribe product characteristics with which compliance is mandatory . Technical regulations can include labeling requirements, import bans, or prohibitions that are related to product characteristics. Standards are documents that have been approved by a recognized body, and prescribe product characteristics with which compliance is voluntary . CAPs are procedures, such as those related to testing, verification, inspection, or certification, that are used to ensure that the requirements prescribed by a given standard and/or technical regulation are satisfied. The TBT Agreement lays out obligations that WTO members must adhere to when enacting technical regulations, standards, and CAPs. These obligations can be enforced through the WTO's dispute settlement procedures established by the DSU. Therefore, a country may request the establishment of a WTO dispute settlement panel to determine whether another party's measure violates the terms of the TBT Agreement. To date, most of the WTO disputes involving the TBT Agreement, including U.S. – COOL and U.S. – Tuna II , have focused on the provisions concerning technical regulations. These provisions are contained in Article 2 of the Agreement, which is the focus of this report. Article 2 of the TBT Agreement contains various requirements that WTO members must adhere to when issuing technical regulations. Article 2 requires that a party shall remove technical regulations that are no longer necessary due to changed circumstances; shall base their technical regulations on accepted international standards, when appropriate; shall explain the justification for such regulations when another party so requests; and shall participate in the creation and adoption of international standards with a view toward harmonizing technical regulations. members must also ensure that their measures are not "more trade restrictive than necessary" to fulfill a legitimate government objective. Furthermore, Article 2 of the TBT agreement contains numerous provisions that call for increased transparency among members with regard to technical regulations. Arguably the most significant obligations, at least with regard to recent litigation that has occurred, are found in Article 2.1 of the TBT Agreement. Article 2.1 requires that countries comply with "national treatment" obligations and "most-favored nation" (MFN) obligations. National treatment obligations provide that a country's technical regulations may not treat foreign products less favorably than like products of domestic origin. MFN obligations require that technical regulations treat products from one foreign country no less favorably than products from other foreign countries. The Appellate Body found, in U.S. – COOL and U.S. – Tuna II , that the U.S. labeling programs violated these prohibitions on discrimination. Before analyzing how the WTO Appellate Body has evaluated certain labeling requirements under Articles 2.1 of the TBT Agreement, it is worth pointing out that the TBT Agreement, unlike other WTO agreements, does not provide any explicit exceptions to these obligations.