商法
Legal positivism became the dominant legal theory of 18th century and found its way into international legal philosophy. At the time, Cornelius van Bynkershoek asserted that the bases of international law were customs and treaties commonly consented to by various states. John Jacob Moser emphasized the importance of state practice in international law. Georg Friedrich von Martens, published the first systematic manual on positive international law, "Precis du droit des gens moderne de l'Europe". During the 19th century, positivist legal theory became even more dominant due to nationalism and the Hegelian philosophy. International Commercial law became a branch of domestic law: private international law, separate from public international law. Positivism narrowed the range of international practice that might qualify as law, favouring rationality over morality and ethics. The 1815 Congress of Vienna marked the formal recognition of the political and international legal system based on the conditions of Europe.