Final answer:
John Selden published 'Mare Clausum' in 1635, a legal treatise that argued for the concept of territorial waters and against the idea of the sea as international territory.
Step-by-step explanation:
In 1635, John Selden, an English jurist, published 'Mare Clausum' (The Closed Sea). This was a legal treatise on the law of the sea, which argued against the Dutch theory of Mare Liberum, proposed by Hugo Grotius, that the sea was international territory and all nations were free to use it for seafaring trade. Selden's work asserted that the sea was, in parts, sovereign territory and could be claimed by nations, establishing the concept of territorial waters.