The question of who owns the sea and how regimes to govern it should be established and managed has been a subject of debate among lawyers and scholars for centuries. Following the âdiscoveryâ of America by Christopher Columbus in 1492 and the first circumnavigation of the globe by Ferdinand Magellan and Juan Sebastian Elcano, completed by the latter in 1522, the full extent of the ocean planet was first realised in Europe. The subsequent intensification of exploration and commerce led to a growing entanglement of ocean spaces, making questions surrounding âthe law of the seaâ more pressing than ever on a global scale.
The Dutch jurist Hugo de Groot, also known as Hugo Grotius, is widely credited with launching the great debate on the freedom versus the dominion of the seas through his work Mare liberum (1609). This brief treatise argued that ocean areas were immune from claims of dominion and that freedom of navigation was a natural right of all peoples and nations. Grotiusâ thesis was countered by John Seldenâs Mare clausum (1635), which justified the possibility of national occupation of, and dominion over, ocean spaces. This debate, which from the late nineteenth century onwards became known as the âbattle of the booksâ, continues to dominate modern scholarship on the early modern law of the sea.
The extensive historiographical output sparked by the battle of the books has placed Mare liberum and its arguments for a free sea at the forefront. Consequently, scholars advocating sovereign claims over the sea are often portrayed as merely responding to Grotiusâ work and its legal arguments. This dominance of the Grotian perspective in scholarship on the law of the sea is frequently taken for granted. Not so by the Italian legal historian Stefano Cattelan, whose aim is not to view arguments in favour of exclusive maritime rights simply as reactions to the notion of mare liberum, but to trace their development on their own terms. To do so, he introduces the concept of âclaimed seasâ, encompassing what Selden would later explicitly term mare clausum, or the closed sea. According to Cattelan, both the development of claims over the sea in the âpre Grotianâ period as well as the scholarly production defending the notion of mare clausum in the seventeenth century have been âobscuredâ due to âa bias considering the development of the law of the sea as a complete victory of the freedom of the seasâ and âby the long-lasting ascendancy of the Dutchman among later generations of jurists and the central place he acquired in the western legal tradition canonâ. (p. 21)
Cattelanâs approach to the âclaimed seasâ encompasses a range of legal and political concepts, including for example âjurisdictionâ ( jurisdictio), âoccupationâ (occupatio), âpowerâ (imperium), âownershipâ (dominium), prescription (praescriptio), and âsovereigntyâ. Legal and political questions relating to the sea, its governance and its legal underpinnings shaped various and sometimes conflicting or even adverse definitions of these concepts. Cattelanâs principal aim is to explore how the âclaimed seasâ principle and its historical variations were employed in legal argumentation to justify claims over maritime spaces. The present book, which is the fruit of this endeavour, delivers several important contributions to the historiography on the law of the sea. Four of these will be touched upon here. They concern time, maritime space, the wider context of power politics, and present-day relevance.
First then, the book puts the freedom versus the dominion of the seas debate in a much wider time frame than usually is the case. The book crosses both the traditional boundary between the Middle Ages and the early modern period, and the cesura created by the publication of Mare liberum in 1609. The former crossing fits well in a current tendency in the historiography of the early modern period, which extends the early modern era backward, including part of the fourteenth and fifteenth centuries, as Hamish Scott recently observed in his introduction to the Oxford Handbook of Early Modern History, 1350â1750 (2015). International legal historians have embraced this approach, including Martti Koskenniemi, whose magnum opus To the Uttermost Parts of the Earth. Legal Imagination and International Power 1300â1870 (2021) starts in the early fourteenth century.
By also crossing the 1609 cesura, Cattelan wants to emphasise that âthe notion of âclaimed seasâ continued to be central in state practice in the decades following the publication of Mare liberumâ (p. 21â22). This is crucial as the distinction between the territorial and the free sea is not just an intellectual construct of the seventeenth century. This distinction has a much longer history which is rooted in customary law. Both classical and medieval scholars influenced the thinking of early modern international lawyers on the law of the sea, even though the revival of classical scholarship in the Renaissance often hid the support from customary law for the law of nations. Claims over specific sea areas were quite common in the Middle Ages: Venice claimed the Adriatic and Genoa the Ligurian Sea. Baldus de Ubaldis (1327â1400) referred to these pretensions as âinveterate customâ. The count of Flanders claimed control of the sea in front of the Flemish coast, known as the Vlaamse stroom (Flemish stream), from at least the middle of the fourteenth century. Further north, Denmark-Norway claimed the northern seas from Norway to Greenland. How these claims were originally recognised by foreign powers and how the latterâs attitudes changed over time is one of the many aspects of the medieval âlaw of the seaâ, which is highlighted in this book, and which show its relevance for the subsequent period.
Second, Cattelanâs study extends beyond a single maritime region to encompass three different maritime spaces, which he refers to as âmacro-regionsâ: the seas of northern Europe, the Mediterranean, and the oceans. Often, the discussion of the âbattle of the booksâ is limited to Grotius and Selden and their respective works in the context of Anglo-Dutch rivalry on the North Sea and the English Channel. This is partly due to the Anglophone domination of academia. Whereas a vast amount of literature is available on Grotius, Selden, and Anglo-Dutch maritime rivalry in English, both the French and Italian historiography on the Mediterranean and the Portuguese and Hispanic historiography on the Iberian division of planet ocean have not been fully integrated in Anglophone literature on the history of the law of the sea. This is especially true for the Venetian/Adriatic and Nordic/Scandinavian dimensions of the debate. Thanks to his mastery of many languages, Stefano Cattelan has been able to integrate these different historiographies into a single analysis, which greatly broadens the scope of understanding the development of legal thinking on how the sea could or should be governed.
Third, the author does not study the development of the âclaimed seasâ principle in a legal vacuum but in the context of power politics. He investigates the constant interplay between the development of doctrine around the âclaimed seasâ on the one hand and state practice on the other. This allows him to fully appreciate the globalisation of the law of the sea as a process which began in the late Middle Ages and which remained relevant for the early modern battle of the books. After all, the oceans became involved in a power struggle between Spain and Portugal in the late fifteenth century, which generated debate among legal scholars. The papal bull Inter caetera and the treaty of Tordesillas at the end of the fifteenth century and the treaty of Zaragoza in 1529, dividing the Pacific, are often considered in the historiography on international law as the starting point for the debate on the law of the sea. Portuguese and Hispanic historiography emphasise that the papal bulls of 1493 were the culmination of a whole series of papal bulls, dating back to pope Clement viâs attribution of the Canary Islands to a Castilian prince in 1344. Both Portugal and Spain originally sought and received papal recognition to legitimise their respective claims to vast maritime spaces. In this respect, the Treaties of Tordesillas and Zaragoza marked a new phase, as they were concluded without papal intervention. Nevertheless, both the papal bulls and the treaties remained significant throughout the sixteenth and seventeenth centuries. The division of the oceans between the two Iberian powers remained a central ideological dispute, not only between them but also with their European rivals. The pope and the Iberian monarchies thus played a crucial role in shaping the closed sea principle, applying it on a global scale, more than a century before the publication of Mare liberum.
Lastly, Stefano Cattelanâs book on the âclaimed seasâ principle is highly pertinent for understanding contemporary trends and developments in the law of the sea. While it is true that the notion of the open sea as inherently free and beyond the sovereignty of any single state has been a cornerstone of modern international law â culminating in the 1982 United Nations Convention on the Law of the Sea â there exists an equally important counter-narrative. Maritime freedoms are enumerated in numerous treaties and an extensive body of regulations worldwide, governing areas such as fisheries, biodiversity, and the Polar regions. Yet, the âclaimed seasâ principle (or mare clausum) has gained increasing prominence in recent years, as exemplified by mounting disputes over maritime zones, with particular attention drawn to Chinaâs claims in the South China Sea. These claims, underpinned by historical justifications extending back to the Eastern Han dynasty (25â220 ce), underscore the enduring role of history in shaping contemporary legal arguments. Determining the validity of such claims requires a nuanced understanding of history, including distant historical contexts that are often overlooked in Western societies, where fleeting present-day concerns frequently dominate discourse. The writing of history tends to ebb and flow in response to current events, and the historiography of the law of the sea is no exception. The present book delivers a major contribution to the turn of the tide in the current debate on the law of the sea. I expect it to play an important role in shaping ongoing discussions of the history, the present, and the future of the law of the sea.
Louis Sicking
Aemilius Papinianus Professor of History of Public International Law, Vrije Universiteit, Amsterdam