Obama slapped a 35% tariff on Chinese tires not too long ago. Presidents have the power to do it unilaterally. Still waiting for the trade war.
The Harmonized Tariff Schedule of the United States (HTS) was enacted by Congress and made effective on January 1, 1989, replacing the former Tariff Schedules of the United States. The HTS comprises a hierarchical structure for describing all goods in trade for duty, quota, and statistical purposes. This structure is based upon the international Harmonized Commodity Description and Coding System (HS), administered by the World Customs Organization in Brussels ; the 4- and 6-digit HS product categories are subdivided into 8-digit unique U.S. rate lines and 10-digit non-legal statistical reporting categories. Classification of goods in this system must be done in accordance with the General and Additional U.S. Rules of Interpretation, starting at the 4-digit heading level to find the most specific provision and then moving to the subordinate categories.