Final answer:
In 1609, Hugo Grotius published 'Mare Liberum' or 'The Freedom of the Seas', which argued for the free use of the seas and laid the foundation for international maritime law.
Step-by-step explanation:
In 1609, Dutch lawyer and philosopher Hugo Grotius published the seminal work Mare Liberum, or The Freedom of the Seas. This text laid the groundwork for international law by arguing for free trade and the open use of the seas. It was revolutionary at the time because it challenged the notion that seas could be owned by nations, a common belief held due to the various imperial claims on large swathes of the world's oceans. Grotius's work had a significant impact on the development of international maritime law and was influential for centuries to come. He is also known for his contributions to natural law and just war theory, aspects that are reflected in his later work, De Jure Belli ac Pacis (On the Law of War and Peace).