Mare clausum

The papacy helped legitimize and strengthen these claims, since Pope Nicholas V by the bull Romanus Pontifex of 1455 prohibited others to navigate the seas under the Portuguese exclusive without permission of the king of Portugal.

This policy was refused by European nations like France, Holland and England, who were then barred from expanding and trading, and engaged in privateering and piracy of routes, products and colonies.

One chapter of his long theory-laden treatise entitled De Jure Prædæ made it to the press in the form of the influential pamphlet, Mare Liberum (The Free Sea).

[10] Despite his arguments, the international situation demanded an end to the Mare clausum policy, and freedom of the seas as an essential condition for the development of maritime trade.

[11] England, competing fiercely with the Dutch for domination of world trade, opposed Grotius' ideas and claimed sovereignty over the waters around the British Isles.

In Mare clausum (1635) John Selden coined the term, endeavoring to prove that the sea was in practice virtually as capable of appropriation as terrestrial territory.

A workable formula was found by Cornelius van Bynkershoek in his De dominio maris (1702), restricting maritime dominion to the actual distance within which cannon range could effectively protect it.