The main query of this contribution concerns the circumstances and conditions under which the concept of jus gentium as it existed in Roman law is included in or excluded from the historical canon of international law. Paradoxically, according to the major twentieth-century handbooks on the history of international law the term ‘law of nations’ derives from the Latin jus gentium. However, historians of international law tend to indicate the jus gentium does not amount to any ‘international law’ in the modern sense. The contribution argues that the idea of the Roman jus gentium as equivalent to our modern international law was rediscovered in the 1930s and 1940s, first by a group of leading Roman law scholars who were ousted from Germany by the Nazi regime, and second by a larger group of thinkers and academics they came into contact with in their new academic surroundings. The reason for this rediscovery is a change in the definition of ‘international law’ especially beyond legal positivism, to encompass two qualities the Nazis despised: individualism and universalism. The purpose of the contribution is to show an instance of a change in canon due to the political circumstances, one with consequences for the formation of actual institutions in international law.