Enhanced De Facto Constraints Imposed by Non-legally Binding Instruments and Interactions with Normative Environment: An Analysis of the Joint Statements for the Conservation and Management of Japanese Eel Stock

Abstract Since 2012, Japan, China, South Korea, and Chinese Taipei have consecutively held informal consultation meetings to discuss the conservation of Japanese eel stock. As a conservation and management measure, these participants adopted the Joint Statement in 2014 to regulate the initial input of Japanese eel seeds into aquaculture ponds. Despite the fact that the input limits were de facto constraints, these measures were implemented as domestic legal regulations in each participant's jurisdiction. This study examines the nature of the de facto constraints imposed by the Joint Statement for conserving and managing Japanese eel stock as a case study of stock regulations. This study further explores the possibilities of strengthening the de facto constraints through interactions with the normative environment; that is, the principle of sustainable development, domestic laws, and the relevant provisions in the United Nations Convention on the Law of the Sea (UNCLOS).