This paper analyzes the distinction between GATT dispute settlement mechanism and the WTO dispute settlement mechanism. To highlight the distinction, it explains the state of historical development of GATT and the WTO. As one of the most important features of the WTO dispute settlement system, it establishes jurisprudence that is unique in the domain of international law. Like constitutional review of domestic laws and declaring laws inconsistent with the constitution ultra vires, the WTO dispute settlement mechanism authoritatively decides about the compatibility of the disputed domestic laws and policies with the WTO rules. When the disputed domestic laws and policies are found inconsistent with the WTO rules, the Dispute Settlement Body of the WTO issues mandatory instructions to its Member bring the inconsistent laws and policies consistent with the WTO rules.