On October 20, 2023, the U.S. Supreme Court ruled in a 6-3 decision that President Donald Trump's use of the International Emergency Economic Powers Act (IEEPA) to impose reciprocal tariffs was unconstitutional. This ruling is particularly notable because it comes from a Supreme Court predominantly appointed by Republican presidents, marking an unexpected check on the Trump administration's key economic policies. Chief Justice John Roberts emphasized that while Congress may grant the president the power to regulate imports, it does not extend to levying tariffs, which are clearly within Congress's taxing powers as stipulated in Article I, Section 8 of the Constitution.

The implications of this decision are profound, as it renders invalid the reciprocal tariffs that the Trump administration had imposed on various trading partners, including basic tariffs of 10% universally applied, as well as higher tariffs on specific countries like Canada, Mexico, and China, under the pretext of emergency economic powers. The ruling highlighted that the powers claimed by the president had gone beyond any historical precedent concerning the IEEPA. Additionally, the court invoked the Major Questions Doctrine, which asserts that significant regulatory authority over the economy should originate from a clear delegation of power from Congress.

The dissenting opinion from the three liberal justices argued that the application of the Major Questions Doctrine was unnecessary, insisting that a straightforward interpretation of the law was sufficient to reach the conclusion of illegality. Nevertheless, this ruling reflects a critical transition in U.S. trade policy interpretation and the balance of powers between the executive and legislative branches, likely reshaping future economic strategies and negotiations in international trade.