Teaching the Law of Nations in King Leopold’s Foreign Office: Léon Arendt’s Droit des gens-course (1903)

This chapter explores Léon Arendt’s 1903 course on international law (Droit des gens), preserved in the Belgian State Archives. The manuscript provides insights into the legal training of Belgian diplomats during a period marked by imperialism, nationalism, and geopolitical uncertainty. Unlike formal publications, these course notes—intended for internal use—reflect practical instruction tailored to diplomats’ needs.

Arendt’s work emphasizes the historical evolution of international law, linking its origins to the Christian Middle Ages and highlighting its progressive development, particularly through treaties and conventions among “civilized” states. His analysis incorporates natural and positive law, arguing that international law relies on reason and consensus, though its application varies across states based on civilizational criteria.

Belgium’s diplomatic practice during the Belle Époque, including its role in shaping international law, are contextualized. Arendt connects this legacy to Belgium’s colonial ambitions, particularly in the Congo Free State, where international legal frameworks were used to justify exploitation under the guise of humanitarianism.

The chapter focuses on two key themes in Arendt’s treatise: the concept of neutrality and the interplay between diplomacy and international law. Arendt distinguishes between voluntary and perpetual neutrality, elaborating on states’ obligations and the influence of great power guarantees. He views war as a legitimate sanction for violations of neutrality and underscores the balance of power and public opinion as mechanisms for maintaining order.

Arendt’s course synthesizes legal doctrine and state practice, equipping diplomats with persuasive tools to navigate complex international relations. The text reflects the intersection of law, politics, and colonial interests, highlighting the enduring tension between moral ideals and pragmatic statecraft in early 20th-century diplomacy.