Postscript to Mr. Trump’s Tariff War: U.S. Supreme Court Rules Trump’s “Liberation Day” Tariffs Are Unconstitutional

On February 20, 2026, by a vote of 6 to 3, the U.S. Supreme Court ruled that Mr. Trump’s Liberation Day tariffs were illegal. While not eliminating the Trump administration’s ability to impose new tariffs, the ruling will substantially curtail Mr. Trump’s ability to levy tariffs at will. Most of the other legal provisions for implementing tariffs require government studies before they can be implemented, so the President will no longer be able to change tariff policies from day to day as he has often done in the past. They also limit the reasons that he can use to justify tariffs. The only tariff that he could enact on his own requires no discrimination across countries, unlike his Liberation Day tariffs. While Mr. Trump announced immediately that he was implementing a tariff surcharge under this authority, these tariffs can be implemented only for five months without the approval of Congress, and we argue that the legal conditions necessary for this import surcharge are not met.