From the Introduction: "In general, the rules of the World Trade Organization (WTO), of which the United States is a member, require each member to apply tariffs and duties equally to all other members. This principle, known as unconditional most-favored-nation (MFN) treatment, has been central to the rules-based global trading system since 1947 and part of U.S. law and foreign policy since 1922. The WTO agreements allow exceptions to this treatment in certain circumstances, including to remedy unfair trade practices and to help domestic industries adjust to sudden surges of fairly traded goods. The three most frequently applied U.S. trade remedy laws permit the imposition of antidumping duties, countervailing duties, and safeguards. These laws are enforced through administrative investigations and actions of two U.S. government agencies: the International Trade Administration of the Department of Commerce (ITA) and the U.S. International Trade Commission (USITC). The most commonly used of these remedies are antidumping (AD) laws. AD laws provide relief to domestic industries that have been, or are threatened with, material injury caused by imports sold in the U.S. market at prices that are shown to be less than fair value. The relief provided is an additional import duty, calculated by the ITA and placed on the dumped imports. Antidumping orders are the most frequently used and the most controversial trade remedy."
CRS Report for Congress, R46296
Congressional Research Service: https://crsreports.congress.gov/