Nations that negotiated trade deals with President Trump are demanding clarity from the U.S. and scrutinizing their options after the Supreme Court struck down tariffs that formed the backbone of the agreements. Mr. Trump and his team said the deals remain in full effect, and they would backfill the tariffs canceled by the justices. Indeed, Mr. Trump swiftly imposed a global tariff of 15% under alternative authorities. Yet the evaporation of Mr. Trump's tariff powers under the International Emergency Economic Powers Act left trading partners wondering what's next, and whether they can secure better terms for their companies. Many countries had struck trade deals in principle but had not fully ratified the pacts, which largely hinged on goodies for the U.S. economy in exchange for a lower tariff rate under IEEPA.