The sixteenth and early seventeenth centuries marked a deep crisis of the international political and legal order of Europe, caused by the Reformation, the emergence of some strong composite monarchies and the discovery of the New World. The chapter maps how the law of nations began to emerge as a new paradigm for the governance of Europe under whose wings rulers, diplomats and scholars attempted to advance claims to an exclusive jurisdiction over international relations by sovereign princes and republics. As such, the ‘law of nations’ functioned as a lever, an argument for power in a period of great clashes between centralising governments, opposing confessions, and regional and local elites, rather than representing a reality. The ultimate success by governments in several important states at the end of the Renaissance was facilitated to a great extent by the patrimonial and transactional nature of the states that allowed to include old, autonomous powers in the machinery of state.