How did Grotius’s idea of freedom of the seas affect international law?

Hugo Grotius’s doctrine of freedom of the seas—first articulated in his 1609 work Mare Liberum—fundamentally challenged the prevailing practice of maritime states asserting sovereignty over vast portions of the ocean. By arguing that the high seas should be open to all nations for trade and navigation, Grotius provided a critical legal framework that countered monopolies claimed by powers like Spain and Portugal.12

While initially a tool to defend Dutch commercial interests, this concept became a cornerstone of international law. Although it did not gain universal acceptance as a formal principle until the 19th century, it eventually evolved to protect essential rights such as freedom of navigation, fishing, and the laying of submarine cables. Grotius’s work helped shift the global order toward a system of relations between sovereign states, establishing a normative foundation that remains central to modern maritime governance and the regulation of the high seas.132