" Each of the contracting States shall permit the navigation of the airships of the other contracting States within and above its territory, reserving the restrictions necessary to guarantee its own safety and that of the persons and property of its inhabitants".
The restrictions referred to relate chiefly to the question of certain zones, over which, if they are properly indicated in advance, no airship may fly unless compelled to by necessity. If an aeroplane is carried by accident or by adverse air conditions over an interdicted zone, it must descend at once and indicate its disability. It must also descend if signalled to from the earth.
The matter of jurisdiction over crimes committed by airmen or their passengers is likewise a matter of international concern. Fauchille has proposed that crimes committed on air-craft "fall under the competence of the tribunals of the nation to which the air-craft belongs." American and English lawyers will object to any such principle because Anglo-Saxon law has always been territorially administered. Probably concurrent jurisdiction will be agreed upon, as in the case of crimes committed on foreign vessels in territorial waters.
Besides crimes committed on air-craft, there are also crimes committed on the ground which involve the rights of airmen. Balloons have been shot at in pure wantonness. Jurisdiction in such cases obviously belongs to the country in which the firearms were discharged. If a man is killed in a flying-machine in the United States by a bullet discharged over the borderline in Canada, there is no reason why murder has not been done in the United States and why the murderer should not be extradited and tried in a United States court.
Lastly, there remains to be considered the legal status of the airship and the aeroplane in time of war. Balloons were used in war long before the dirigible airship or the aeroplane were brought to a state of practical perfection, but they never played so conspicuous a part in military operations that it was necessary to define their status according to the principles of international law. It is true that Bismarck said that an Englishman who manned a French balloon would be subject to arrest and trial " because he had spied out and crossed our outposts in a manner which was beyond the control of the outposts, possibly with a view to making use of the information thus gained to our prejudice." That dictum of blood and iron seems much too drastic even to German commentators. A spy is supposed to act clandestinely. An air-craft is so conspicuous an object that even though bent on ascertaining the enemy's strength and the disposition of its forces, its errand can hardly be secret. On the other hand, Mr. Kuhn has pointed out that the impossibility of flying secretly by day, at least, is in itself no reason why the use of the aircraft may not be clandestine. The Hague Peace Conference in 1907 left the matter in a very unsatisfactory condition. It provided that aeronauts were not to be regarded as spies if they carried despatches or maintained communication between different parts of an army or territory, but it failed to fix the status of the reconnoitring airman. In the war of the future the aeroplane and the airship will perform much the same function as a cavalry reconnaissance in force; yet even Bismarck would not have shot as a spy a trooper captured on a scouting raid. The international complications which may arise even at the present time will undoubtedly be considered when the next Hague International Conference takes place. The possibility that an alert military spy, floating serenely over a fortress which has cost a nation millions, may photograph or sketch every battery, manifestly necessitates the adoption of some restrictive measures. So jealously are many of the fortifications of Europe guarded from the watchful eyes of spies, that entry within their portals is granted only on certain conditions. No cameras may be taken within the lines; nor is admission granted without credentials. What a spy on land might be unable to discover in months by cunning, cajolery, and bribery, will be exposed to an aeronaut in half an hour. Some check must therefore be placed upon the scout in the air. At the International Conference on Aerial Navigation of 1910 it was proposed that a state should have the privilege of developing photographic negatives found on board an airship coming to earth in its territory, and if necessary to seize them and the photographic apparatus. Wireless telegraphic instruments, too, could not be used, according to another provision, without special permission, for any other purpose than to secure the vessel's safety. Perhaps, although no International Conference has thus far suggested it, the pilots of the future will be constrained to avoid fortifications entirely, or run the risk of arrest by air sentry, — military lookouts gliding along in aeroplanes ready to act if a too closely approaching atmospheric tourist appears. Arrests will undoubtedly be made by these sentinels in the air; the captured aeronaut will be asked for his credentials and will be searched for sketches that may implicate him. If he is caught red-handed, he will be punished how, must be determined by international agreement.
The war of the future will be a conflict of aircraft as well as of infantry and artillery. How shall the aeroplane of any warring country be distinguished from those of any other? Every ship on the high seas, whether it be merchantman or battleship, flies the flag of its country, a challenge to its foes in time of war, a badge of peace to its friends. The question of nationality brought up some interesting points during the International Conference of 1910. It was decided that it should be determined by the nationality of the owner or by his domicile. It was also voted that:
" A State may require its subject to be at the same time domiciled on its territory, or it may admit domiciled foreigners as well as its subjects. Airships belonging to companies must take the nationality of the State in which their head office is situated. In the case of an airship belonging to several owners, at least two-thirds must be owned by subjects of, or foreigners domiciled in, the State conferring nationality".