Tariffs are the most flexible, peaceful, and effective policy instrument to regulate importation. That’s the economic, diplomatic, and common-sense context as the Supreme Court considers whether presidents have the authority to use tariffs under the International Emergency Economic Powers Act (IEEPA). The plaintiffs assert IEEPA can’t be stretched to include tariffs because, although IEEPA empowers the president to “regulate … importation” of property in an emergency, it makes no mention of the word “tariffs.”...