The reason that wireless messages and cable messages require different treatment by a neutral Government is as follows:
Communication by wireless cannot be interrupted by a belligerent. With a submarine cable it is otherwise. The possibility of cutting the cable exists, and if a belligerent possesses naval superiority the cable is cut, as was the German cable near the Azores by one of Germany's enemies, and as was the British cable near Fanning Island by a German naval force. Since a cable is subject to hostile attack, the responsibility falls upon the belligerent, and not upon the neutral, to prevent cable communication.
A more important reason, however, at least from the point of view of a neutral Government, is that messages sent out from a wireless station in neutral territory may be received by belligerent warships on the high seas. If these messages, whether plain or in cipher, direct the movements of warships or convey to them information as to the location of an enemy's public or private vessels, the neutral territory becomes a base of naval operations, to permit which would be essentially unneutral.
As a wireless message can be received by all stations and vessels within a given radius, every message in cipher, whatever its intended destination, must be censored, otherwise military information may be sent to warships off the coast of a neutral. It is manifest that a submarine cable is incapable of becoming a means of direct communication with a warship on the high seas; hence its use cannot, as a rule, make neutral territory a base for the direction of naval operations.
(2) Censorship of mails and in some cases repeated destruction of American letters on neutral vessels.
As to the censorship of mails, Germany, as well as Great Britain, has pursued this course in regard to private letters falling into their hands. The unquestioned right to adopt a measure of this sort makes objection to it inadvisable.
It has been asserted that American mail on board of Dutch steamers has been repeatedly destroyed. No evidence to this effect has been filed with the Government, and therefore no representations have been made. Until such a case is presented in concrete form this Government would not be justified in presenting the matter to the offending belligerent. Complaints have come to the department that mail on board neutral steamers has been opened and detained, but there seem to be but few cases where the mail from neutral countries has not been finally delivered. When mail is sent to belligerent countries open and is of a neutral and private character it has not been molested so far as the department is advised.
(3) Searching of American vessels for German and Austrian subjects on the high seas and in territorial waters of a belligerent.
So far as this Government has been informed, no American vessels on the high seas, with two exceptions, have been detained or searched by belligerent warships for German and Austrian subjects. One of the exceptions to which reference is made is now the subject of a rigid investigation, and vigorous representations have been made to the offending Government. The other exception, where certain German passengers were made to sign a promise not to take part in the war, has been brought to the attention of the offending Government with a declaration that such procedure, if true, is an unwarranted exercise of jurisdiction over American vessels in which this Government will not acquiesce.
An American private vessel entering voluntarily the territorial waters of a belligerent becomes subject to its municipal laws, as do the persons on board the vessel.