In 1821 Russia claimed that the Pacific north of latitude 51° was mare clausum.
In mare clausum John Selden endeavoured to prove that the sea was practically as capable of appropriation as territory.
Whence it is clear that Denmark had given Napoleon grounds for hoping that she would declare the Baltic a mare clausum.
Selden's mare clausum was a reply, written by the king's command, to the Mare liberum.
This doctrine in the History of International Law is known as that of mare clausum, or “closed sea.”
mare clausum merely means the place where they catch the seals, you know; mare, Latin for sea.