The role of international organizations in the dissemination of ideas has been widely recognized by constructivist scholars. However, the question of how international organizations influence sovereign states has not been well answered. The classical constructivist discourse provides some good insights, particularly into the relationship between the principle of state sovereignty and the collective identity of states. And the field of international law, which is closely related to international organizations, has been introduced into the consideration of constructivist scholars. In the post-cold-war, the ever-changing international community, examples of the application of this unique approach are constantly being found. As a region with a weak sense of historical identity, the Balkan states provide a good example for the theory of international organizations constructing national identity and interests. Croatia is one of the most representative countries. By joining the WTO, great progress has been made towards the goal of economic and security integration with Europe. It showed that international organizations can influence sovereign states to accept their ideas. The working model of this fact is to negotiate the acceptance by the state of the provisions of the basic documents of the organization and to force the state to comply through a series of corresponding procedures. This article uses historical and documentary methods to sort out the documents related to it, using historical materials from the English world and Croatia academia. The perspective of constructivism is also an important component of the research method. Future studies may further explore the mechanism of this mode of influence and apply this paradigm of international organization and international law to more and more literature and empirical studies.