The GATT treaty's loophole for free trade areas in Article XXIV has puzzled and deceived prominent scholars, who trace its postwar origins to US aspirations to promote European integration and efforts to persuade developing countries to endorse the Havana Charter. Drawing from archival records, this article shows that in fact US policymakers crafted the controversial provisions of Article XXIV to accommodate a trade treaty they had secretly reached with Canada. As a result, the free trade area exemption was embedded in the GATT–WTO regime, even though neither the Havana Charter nor the US–Canada free trade agreement was ever ratified. Theoretically, the case is an important example of how Cold War exigencies altered the policy ideas of US officials.