Financial markets, which have whipsawed wildly in response to every twist and turn in Trump's chaotic trade war, reacted with cautious optimism on Thursday, a day after the U.S. Court of International Trade ruled that Trump overstepped his authority in imposing punitive tariffs on virtually every country in the world.

OTTAWA—Prime Minister Mark Carney hailed a U.S. court decision that ruled against President Donald Trump’s “unjustified” use of emergency powers to slap sweeping tariffs on American trading partners. But Carney said other equally offensive tariffs and threats remain.

OTTAWA — Canada is breathing a cautious sigh of relief after the U.S. Court of International Trade ruled that U.S. President Donald Trump does not have the authority to impose sweeping tariffs or fentanyl-related duties on its trading partners.