The set of articles in this dossier is the result of a workshop held in June of this year at the University of Amsterdam under the auspices of Grotiana, and co-organized by the nwo-funded ‘Servus’-project and the Paul Scholten Centre for Jurisprudence. The workshop titled ‘Arguing over Empire: Hugo Grotius, European Expansionism and Slavery’ is part of a series of conferences organized by the Grotiana Foundation preceding the celebration in 2025 of the 400th anniversary of Grotius’s opus magnum On the Law of War and Peace (De iure belli ac pacis) first published in 1625. Based on this work, Grotius is generally regarded as one of the ‘founding fathers of modern international law’. However, he was also one of the early architects of Dutch colonial and imperial rule in the East Indies. Between 1604 and 1615, he served the Dutch East India Company (voc) as a legal advisor and political lobbyist. In this capacity, he wrote memoranda and policy documents providing legal and political justifications for the Company’s commercial and military activities in monsoon Asia. In 1604, Grotius was commissioned by the voc to write a treatise to defend the seizure of a Portuguese vessel off the coast of Johor (present-day Singapore). In the only chapter of the treatise published during his lifetime, titled The Free Sea (Mare Liberum), he argued that the Portuguese violated the natural rights of the Dutch by preventing them from sailing to the East Indies and engaging in trade with indigenous populations.

Grotius’s On the Law of War and Peace is another case in point. Although the author was an exile in Paris by then, he relied on many years of practical experience as a voc advisor and lobbyist in writing his magnum opus. In On the Law of War and Peace, he elaborates the views presented in On the Law of Prize and Booty by conceptualizing the natural rights to travel and free passage, the rights to settle in uninhabited lands and use natural resources, and the right to free trade between ‘persons at a distance’, invoked by Europeans to demand access to non-European markets and territories. On the Law of War and Peace also provides a legal justification of slavery as part of natural law and the law of nations. In Grotius’s view, those who are defeated in a just war can be enslaved under the law of nations, while human beings may also ‘voluntarily’ submit to slavery under natural law. Moreover, under some circumstances the children of the enslaved inherit the unfree status of their parents, according to On the Law of War and Peace. The aim of the workshop was to explore the many connections between Grotius’s thinking about natural law and the law of nations and his full-throated defense of European expansion overseas and slavery. The collaborators in the workshop ‘Arguing over Empire: Hugo Grotius, European Expansionism and Slavery’ were invited to critically examine these connections by addressing the imperialist and colonialist readings of Grotius’s theory of natural rights, just war, property, unequal treaties and alliances, monopoly contracts, slavery, and the role of private actors (e.g., trading companies).

The dossier includes a contribution by Guus van Nifterik, who details the structure of slavery in Grotius under the law of nations. In line with the more general conclusions of Straumann and Iurlaro, Van Nifterik traces the use of ancient sources, legal ones, but also texts from, for example, historians and philosophers. The second contribution in the set dealing with slavery in Grotius, in particular On the Law of War and Peace, is that from Somos, Cleary, Dufour, Jones Corredera and Salerno. Positing slavery as a ‘long-standing puzzle at the heart of Grotian theory’, this contribution is not primarily concerned with the issue of slavery in the works of Grotius himself, but starts off with the later employment of On the Law of War in Peace in cases in English and American common law as well as Spain dealing with the enslaved. The findings are then connected to the spread of and annotations in a number of copies of On the Law of War and Peace, containing notable references and comments on the conception of slavery in Grotius. Moreover, Hasan-Birdwell in her contribution views the influence of Grotius in the practical historical reality of African slave raids. Rather than a just war, Hasan-Birdwell explores whether these raids can find their theoretical footing in Grotius’s concept of ‘solemn war’. Whereas slavery was abolished legally by The Netherlands in 1863, the country remained a colonial power far into the twentieth century. Later theorists of colonialism, such as Cornelis van Vollenhoven, employed Grotius in this context to explain the existence, emergence, and working of customary law as a source of law. This is the topic of the final contribution to the set, by In ’t Veld.