From the Document: "A tariff is a customs duty levied on imported and exported goods and services. Historically, countries used tariffs as a primary means of collecting revenue. Today, other taxes account for most government revenue in developed countries. Tariffs are now typically used to protect domestic industries or as leverage in trade negotiations and disputes. The U.S. Constitution empowers Congress to set tariffs, a power that Congress has partially delegated to the President. The United States is also a member of the World Trade Organization (WTO) and a party to a number of trade agreements, which include specific tariff-related commitments. Congress and the President thus create U.S. tariff policy within the context of a rules-based global trading system. [...] For more than 80 years, Congress has delegated extensive tariff-setting authority to the President. This delegation insulated Congress from domestic pressures and led to an overall decline in global tariff rates. However, it has meant that the U.S. pursuit of a low-tariff, rules-based global trading system has been the product of executive discretion. While Congress has set negotiating goals, it has relied on Presidential leadership to achieve those goals. The Trump Administration was openly critical of low-tariff policies and made extensive use of the authorities delegated to the President to increase tariffs on certain goods imported from key U.S. trading partners with little congressional input. Congress may want to consider whether the current restrictions on such delegated authorities adequately protect congressional interests."
CRS In Focus, IF11030
Congressional Research Service: https://crsreports.congress.gov/