Meaning of the Term "Freedom of the Open Sea."
§ 254. The term "Freedom of the Open Sea" indicates the rule of the Law of Nations that the Open Sea is not and never can be under the sovereignty of any State whatever. Since, therefore, the Open Sea is not the territory of any State, no State has as a rule a right to exercise its legislation, administration, jurisdiction,[499] or police[500] over parts of the Open Sea. Since, further, the Open Sea can never be under the sovereignty of any State, no State has a right to acquire parts of the Open Sea through occupation,[501] for, as far as the acquisition of territory is concerned, the Open Sea is what Roman Law calls res extra commercium.[502] But although the Open Sea is not the territory of any State, it is nevertheless an object of the Law of Nations. The very fact alone of such a rule exempting the Open Sea from the sovereignty of any State whatever shows this. But there are other reasons. For if the Law of Nations were to content itself with the rule which excludes the Open Sea from possible State property, the consequence would be a condition of lawlessness and anarchy on the Open Sea. To obviate such lawlessness, customary International Law contains some rules which guarantee a certain legal order on the Open Sea in spite of the fact that it is not the territory of any State.
[499] As regards jurisdiction in cases of collision and salvage on the Open Sea, see below, §§ [265] and [271].
[500] See, however, above, § [190], concerning the zone for Revenue and Sanitary Laws.
[501] Following Grotius (II. c. 3, § 13) and Bynkershoek ("De dominio maris," c. 3), some writers (for instance, Phillimore, I. § 203) maintain that any part of the Open Sea covered for the time by a vessel is by occupation to be considered as the temporary territory of the vessel's flag State. And some French writers go even beyond that and claim a certain zone round the respective vessel as temporary territory of the flag State. But this is an absolutely superfluous fiction. (See Stoerk in Holtzendorff, II. p. 494; Rivier, I. p. 238; Perels, pp. 37-39.)
[502] But the subsoil of the bed of the Open Sea can well, through driving mines and piercing tunnels from the coast, be acquired by a littoral State. See above, § [221], and below, §§ [287c] and [287d].
Legal Provisions for the Open Sea.
§ 255. This legal order is created through the co-operation of the Law of Nations and the Municipal Laws of such States as possess a maritime flag. The following rules of the Law of Nations are universally recognised, namely:—First, that every State which has a maritime flag must lay down rules according to which vessels can claim to sail under its flag, and must furnish such vessels with some official voucher authorising them to make use of its flag; secondly, that every State has a right to punish all such foreign vessels as sail under its flag without being authorised to do so; thirdly, that all vessels with their persons and goods are, whilst on the Open Sea, considered under the sway of the flag State; fourthly, that every State has a right to punish piracy on the Open Seas even if committed by foreigners, and that, with a view to the extinction of piracy, men-of-war of all nations can require all suspect vessels to show their flag.
These customary rules of International Law are, so to say, supplemented by Municipal Laws of the maritime States comprising provisions, first, regarding the conditions to be fulfilled by vessels for the purpose of being authorised to sail under their flags; secondly, regarding the details of jurisdiction over persons and goods on board vessels sailing under their flags; thirdly, concerning the order on board ship and the relations between the master, the crew, and the passengers; fourthly, concerning punishment of ships sailing without authorisation under their flags.
The fact that each maritime State has a right to legislate for its own vessels gives it a share in keeping up a certain order on the Open Sea. And such order has been turned into a more or less general order since the large maritime States have concurrently made more or less concordant laws for the conduct of their vessels on the Open Sea.