International Law of Customs Unions: Conceptual Variety, Legal Ambiguity and Diverse Practice

Abstract

Abstract Despite having considerable historical presence – traceable from 19th-century Germany – customs unions (CUs) have long been an understudied phenomenon in international law. This article aims to remedy this gap by critically reviewing the concept of customs union and identifying key issues in CU designs. The article problematizes what is understood by the concept of CU and what is entailed by the foremost definition of CUs found in Article XXIV of the General Agreement on Tariffs and Trade (GATT). It further investigates how recurrent design issues are resolved in practice by different CUs considering the inherent tension between the enactment of common rules and institutions and state sovereignty. We find variety in the historical, economic and legal conceptualizations of CUs, ambiguity and lacunas in Article XXIV of the GATT and diversity of CU designs along with a discernible concern for the impact of legal arrangements on state sovereignty.