The General Agreement on Tariffs and Trade (GATT) and its successor, the Word Trade Organization (WTO), have been the main forum of international trade since the end of the Second World War. The regime is unquestionably based on free-market rules and principles. Yet in the last two decades, formerly planned economies — including Eastern European countries, former Soviet countries and China — have attempted to join the GATT/WTO. To encourage their transition under the influence of free-market principles, and to be a truly global trade organization, the GATT/WTO has accepted applicants with a reforming planned economy. This article studies the evolution of the GATT/WTO's approaches to integrate non-market economies and shows that the approach to integrate non-market economies during the WTO era is significantly different than during the GATT. While special mechanisms were provided in GATT accession protocols to bridge different market structures, WTO accessions require non-market economies to convert their own market structures. This article holds that this intolerance of different market structures in the WTO reflects the collapse of embedded liberalism and the rise of coercive trade diplomacy. Multilateral trade diplomacy has therefore become a means of imposing a domestic restructuring of economic structures rather than providing a negotiation forum for trade liberalization.