The international law of the sea is one of the oldest branches of international law.
The foundations of ancient maritime law are linked to the Rhodian Sea Code (Lex Rhodia), dating to around the 8 century A.D. The roots of modern oceans law are often traced to the early 17" century treatise by the Dutch scholar Hugo Grotius titled Mare Liberum (Freedom of the Seas).
The concept of the freedom of the seas became the guiding principle of the law of the sea.
The basic rules of oceans law underwent a transformation starting from 1930, when the League of Nations began its codification work related to the law of the sea.