Emerging State Practice on Maritime Limits: A Grotian Moment Unveiling a Hidden Truth?

The legal order of the oceans has seen rapid developments and paradigm shifts. At least one of them has been described as a textbook example of a Grotian Moment: the emergence of the customary international law on the continental shelf, stemming from increased demand for oil and gas, coupled with technological advances and the Truman Proclamation of 1945. Now, eighty years later, the law of the sea is again faced with fundamental changes as the basis for maritime limits is eroded by sea level rise. State practice, going back at least a century, has demonstrated that maritime limits normally fluctuate with physical changes to the coast. This understanding has not caused significant changes to the extent or location of maritime entitlements in a historical context. However, sea level rise stands to have catastrophic impacts as the submergence of individual coastal features can cause the loss of maritime areas spanning hundreds of thousands of square kilometres. This realisation has ignited a movement to change the law on maritime limits. Around 2010, the first States began to declare that their maritime limits would be stable, notwithstanding subsequent sea level rise. Several States and a coalition of States have since made similar declarations and the study of the ila Committee on International Law and Sea Level Rise indicates that the practice is in a phase of crystallisation. That suggests that new customary international law may be developing and the events leading to these developments might justify the use of the term Grotian Moment, leading to accelerated formation of customary international law or revised interpretation of the current law. The traditional requirements of State practice and opinio juris are not satisfied at present. However, the impacts of sea level rise on maritime limits may represent a moment of discovery that unveils a hidden truth about the law, overriding the traditional interpretation that renders maritime limits ambulatory.