Inaugural Professorial Lecture

A Sea of Tranquillity or an Ocean of Outlaws? Mare Liberum through the Ages

In this lecture, I consider the lasting significance of Hugo Grotius’ concept of Mare Liberum, or "the freedom of the seas". I question the extent to which this foundational principle of international law remains relevant after several significant attempts to regulate the global ocean commons – the free seas – and in light of a number of contemporary global challenges. I begin with the historical context of Mare Liberum, published in 1609, contrasting it with the rival concept of Mare Clausum, and show how the tension between these two paradigms has influenced attempts by states to unilaterally extend their sovereignty into the sea, at the same time as shaping global attempts to legally regulate states’ uses of and impacts upon the seas and oceans. In discussing seminal events in the history of international law, and reflecting on more contemporary global challenges – from illegal fishing, through transnational crime, to global environmental degradation – I will outline both limits and threats to the "free seas" idea (at least as commonly understood), whilst nonetheless still defending its lasting significance and potential as a means for pro-active states to extend the rule of law beyond the realms of national jurisdiction.