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Article I, Section 8 of the U.S. Constitution grants Congress the power to lay and collect tariffs and to regulate commerce with foreign nations.9 The last time that Congress set tariff rates was in 1930.10 Since then, changes to U.S. tariffs have been the result of presidential action using authority Congress delegated through statute to the executive branch.11 Historically, most of these changes have been made by presidential proclamation following U.S. entry into various international trade agreements that generally sought to reduce or eliminate tariffs and nontariff barriers among the parties.12
During the 119th Congress, President Trump has imposed additional tariffs on goods from virtually every U.S. trading partner.13 President Trump has cited two statutes as legal authority to impose these tariffs. Most of the tariffs have been imposed using the International Emergency Economic Powers Act (IEEPA), which authorizes the President to "regulate ... importation," among other authorities, to "deal with" declared emergencies concerning certain "unusual and extraordinary threat[s]" to the "national security, foreign policy, or economy" of the United States.14 The President also has imposed some tariffs using Section 232 of the Trade Expansion Act of 1962, which authorizes the President to adjust imports that the Secretary of Commerce has found threaten to impair national security.15 As a result of tariff actions since January 2025, the U.S. average effective tariff rate as of mid-September 2025 is the highest it has been since the 1930s; according to one estimate, the U.S. overall average effective tariff rate has increased from approximately 2.5% in January 2025 to 17.4% in September 2025.
