A Critical Examination of the Protectorate System under International Law: Focusing on Legal Limitations in the Late 19th and Early 20th Centuries

The purpose of this study is to provide a historical and critical examination of the protectorate system during the era of neo-imperialism in the late 19th and early 20th centuries. This study argues that the jurisprudence of 19th-century protectorates lacked coherent legal rules and was characterized by uncertainty. Unlike previous studies that primarily focused on the invalidity or validity of the Japan–Korea Treaty of 1905, this paper critically analyzes the legal problems inherent in the modern protectorate system itself. In the late 19th century, the protectorate system was viewed as a stepping stone to colonization; in this sense, the protectorate system of the neo-imperialist era possessed a more “civilizing” character than its predecessors. This study points out the structural differences between the protectorate system existing among European states before the 18th century and the 19th-century protectorate system, emphasizing the background of this change and the problems with its international legal jurisprudence. The protectorate theory of the time anticipated annexation and theoretically presupposed a legal doctrine of transferring external sovereignty based on the division of sovereignty. Generally, protectorates were understood as semi-sovereign states where internal autonomy was recognized, but crucial foreign relations were controlled by a great power. However, the legal doctrine of protectorates at the time diverged from the realities of the international community. Since it could not justify or explain all the diverse phenomena of reality, problems with the protectorate doctrine were frequently pointed out, and there was no consensus on the matter. Particularly, the coexistence of natural law theories within the international community at the time made pre-19th-century arguments for protectorates theoretically plausible. Furthermore, conflicting views existed regarding the divisibility and indivisibility of sovereignty, making it difficult to regard any particular perspective as inherently legitimate.