Freedom of the Open Sea and war.
§ 256. Although the Open Sea is free and not the territory of any State, it may nevertheless in its whole extent become the theatre of war, since the region of war is not only the territories of the belligerents, but likewise the Open Sea, provided that one of the belligerents at least is a Power with a maritime flag.[503] Men-of-war of the belligerents may fight a battle in any part of the Open Sea where they meet, and they may capture all enemy merchantmen they meet on the Open Sea. And, further, the jurisdiction and police of the belligerents become through the outbreak of war in so far extended over vessels of other States, that belligerent men-of-war may now visit, search, and capture neutral merchantmen for breach of blockade, contraband, and the like.
[503] Concerning the distinction between theatre and region of war, see below, [vol. II. § 70].
However, certain parts of the Open Sea can become neutralised and thereby be excluded from the region of war. Thus, the Black Sea became neutralised in 1856 through article 11 of the Peace Treaty of Paris stipulating:—"La Mer Noire est neutralisée: ouverte à la marine marchande de toutes les nations, ses eaux et ses ports sont formellement et à perpétuité interdites au pavillon de guerre, soit des puissances riveraines, soit de tout autre puissance." Yet this neutralisation of the Black Sea was abolished[504] in 1871 by article 1 of the Treaty of London, and no other part of the Open Sea is at present neutralised.
Navigation and ceremonials on the Open Sea.
§ 257. The freedom of the Open Sea involves perfect freedom of navigation for vessels of all nations, whether men-of-war, other public vessels, or merchantmen. It involves, further, absence of compulsory maritime ceremonials on the Open Sea. According to the Law of Nations, no rights whatever of salute exist between vessels meeting on the Open Sea. All so-called maritime ceremonials on the Open Sea[505] are a matter either of courtesy and usage or of special conventions and Municipal Laws of those States under whose flags vessels sail. There is in especial no right of any State to require a salute from foreign merchantmen for its men-of-war.[506]
[505] But not within the maritime belt or other territorial waters. See above, §§ [122] and [187].
[506] That men-of-war can on the Open Sea ask suspicious foreign merchantmen to show their flags has nothing to do with ceremonials, but with the supervision of the Open Sea in the interest of its safety. See below, § [266].
The freedom of the Open Sea involves likewise freedom of inoffensive passage[507] through the maritime belt for merchantmen of all nations, and also for men-of-war of all nations in so far as the part concerned of the maritime belt forms a part of the highways for international traffic. Without such freedom of passage, navigation on the Open Sea by vessels of all nations would be a physical impossibility.