Abstract: The violation of Belgium's perpetual neutrality by Germany is a classic topos of diplomatic history in the European theatre of the Great War. The Treaty of London (19 April 1839) was torn up by Kaiser Wilhelm as a "Scrap of Paper". Yet, what were the conception foundations of this sui generis institution of international law? To what extent could this status have been applicable to Congo? International law is not a shortlist of enforceable norms, but an arena wherein states seek legitimation for their political choices. The vagueness of treaty clauses, such as the Treaty of London (1839) or the Berlin Final Act (1885), was both a weakness and a guarantee for the argumentative comprehensiveness of the respective legal regimes. This can be illustrated at two distinct levels. First, Belgian scholars (Nys, Descamps) have been influential in international doctrine (Koskenniemi, Gentle Civilizer of Nations). Second, international affairs were a topos of controversy in the Journal des Tribunaux, the weekly legal periodical created by Edmond Picard and continued by Leon Hennebicq. The traditional sources of international law (treaties, doctrine, custom) reveal multiple positions on the neutrality status of both metropolis and colony. Arendt's landmark treatise on Belgian neutrality (1845) has proven to be prophetic. The shaky foundations of perpetual neutrality reach back to the early modern period. Positivist stances such as those of Liszt (1913) and Oppenheim (1902) could position neutrality as an exception with regards to the standard narrative of state-made international law. This is an important caveat applied to pacifist literature. Further on, patriotic narratives in the Journal des Tribunaux were heavily influenced by foreign doctrine. Both diplomacy and domestic political culture were drenched in legal language, produced by and for the social world of lawyers.