Revue Droit International Public, p. 673, Sept.-Oct., 1909.)

There is also an undisputed legal right to regulate the movement of persons approaching fortifications, whether they approach by land, water, or air.

The use of the wireless telegraph has also been subject to national and international regulation.

Jurisdiction in subjacent State.--The Berlin agreement of 1903 and the Berlin convention of 1906 in regard to wireless telegraphy assume for the more important States of the world that jurisdiction over the atmosphere resides in the subjacent States.

The Hague conventions have prohibited by international agreement the launching of projectiles from balloons, bombardment "by any means whatever" of towns, villages, habitations, or buildings which are not defended and unneutral use of the radiotelegraph.

A dispatch of December 20, 1910, announces that Italy proposes that for time of war, by agreement by joint note, the powers of the world prohibit all firing from and arming of aerial ships, limiting their use to scouting and observation purposes only. This restriction was not made in the Turko-Italian War of 1911-12.

It is evident from the regulations issued by State authority, from decisions of courts, from codes, and expressions of State officials that States assume that they have jurisdiction in the air space above their territory.

The ideas in regard to the limits of aerial jurisdiction set forth by those who are giving special attention to this subject are not, however, in accord. It is natural that one group should maintain the ancient doctrine that "the air is free." Another group maintains that the domain of the air is exclusively in the subjacent State. A third group, between these, maintains that a certain zone of atmosphere above a State is within its jurisdiction, and beyond this the air is free. The height of this zone of jurisdiction is, however, a subject of considerable difference of opinion.

The argument has been advanced that the aerial domain of a State should be limited to a certain distance

above its territory. It has been stated that the altitude which an airship might attain can be determined, but as the limits fixed in earlier estimates have been surpassed it seems unwise to attempt at present to establish such limits.

Some think the height of the zone can be determined in a manner analogous to that of determining maritime jurisdiction. Some see unsurmountable difficulties in the use of this analogy. Of those who favor a zone theory some propose that the zone be determined by the limit of vision; some that the limit of effective control by arms be the determining factor; some that an arbitrary limit be agreed upon by the States of the world; and others advance other propositions.

It is evident that the claim can not be well sustained that the aerial dominion should be regarded as analogous to maritime, and that what is allowed in the marginal sea be allowed in a marginal zone of air, and what may be done on the high sea may be done in the aerial space above this marginal zone. While in time of war a battle between fleets upon the high sea might not endanger any neutral, a contest between their aerial fleets in the high air might result most disastrously to the subjacent neutral. In any case, while the force of gravity remains and until further means for counteracting its operation are devised, a neutral State can not be expected to submit to the risks of such use of the air. A warship upon the high sea when disabled may sink to the bottom without peril to the nearest neutral. From a battle in space above a neutral the descent of the disabled airship, possibly with a load of explosives, would certainly be with peril to the neutral. The perils to innocent neutrals because of war upon the high sea may be exceptional and almost negligible. The perils to innocent neutrals in case of war in the high air above neutral territory would be certain and grave. Indeed, the perils to those who, by the modern laws and customs of war are not liable to undue risks even within enemy territory, would give good ground for a question as to whether aerial battles above belligerent territory even should not be restricted. If

belligerents on the sea may not fight so near the coast that their shot shall fall within neutral jurisdiction, it would seem that battles in the air above neutral jurisdiction would be similarly prohibited. This would apply to the air above land and above the marginal sea, as projectiles or disabled airships would, by the universal physical law, fall toward the center of the earth when unrestrained. As, according to the law of physics, the velocity would be accelerated in proportion to the distance from which a body falls, it would on a physical basis be no less dangerous to allow a free zone at a considerable height than in a lower altitude. While on the sea it might be generally maintained that the greater the horizontal distance from the adjacent State the less probability that the act would affect the adjacent State, it could not be claimed that the greater the vertical distance from a subjacent State the less the probability that the act would affect the subjacent State. This distinctly would not be true in case of anything falling from an airship. Similarly, in observations of fortifications, photography by telescopic lenses, etc., increase of altitude may within limits give a greater range. Submarine mines for the defense of a State may not be visible from the surface of the water but may be seen from an airship.

It would seem that physical safety, military necessity, the enforcement of police, revenue, and sanitary regulations justify the claim that a State has jurisdiction in aerial space above its territory. This position also seems to underlie established domestic law and regulations, the decisions of national courts, the conclusions of international conferences, and the provisions of international conventions.

It would seem wise, therefore, to start from the premise that air above the high seas and territory that is res nullius is free, while other air is within the jurisdiction of the subjacent State "and that the exceptions to this rule are such only as by common usage and public policy have been allowed, in order to preserve the peace and harmony of nations and to regulate their intercourse in a manner best suited to their dignity and rights," and for

these exceptions to the exclusive right of aerial jurisdiction of the subjacent State, international conferences should by agreement immediately provide.

Von Bar's proposition, 1911.-M. von Bar, after consideration of various aspects of the use of air craft in the time of war, submitted to the members of the Institute of International Law in 1911 the following rules:

ARTICLE I. En général il est interdit de se servir des aérostats, ballons or aéroplanes comme moyens de destruction ou de combat.1 ART. 2. Toutefois.

(a) Les aérostats, ballons ou aéroplanes militaire ennemis, si l'on tire sur eux (par des canons placés à terre ou à bord d'un vaisseau) peuvent se défendre.

2

(b) Les combats en l'air sont permis,

(1) S'il y a combat naval et que les aérostats, ballons ou aéroplanes ne sont éloignés que de vingt kilomètres du lieu du combat.

(2) Dans les mers territoriales des belligérants dans une zone de blocus.3

(3) Dans les sphères aériennes enveloppant les territoires des belligérants.

ART. 3. Il est interdit de capturer en l'air des aérostats, etc., privés ennemis, sauf les cas où ils entrent volontairement dans la sphère aérienne du territoire de l'adversaire ou dans une zone de blocus ou dans le cas de contrebande prévu par l'art. 4.

ART. 4. De même il est interdit de saisir et de confisquer des aérostats neutres ou leurs cargaisons à titre de contrebande, sauf le cas où l'on apporte immédiatement des secours à une côte ou à un port bloqué ou à l'armée ou à la flotte ennemie au théâtre de la guerre.

ART. 5. Dans les cas exceptés par les art. 4 et 5 on appliquera les règles des prises maritimes.

1 Peut-être on préférerait une formule conforme à celle de la convention de la Haye. Mais elle ne dirait pas tout ce qu'à mon avis il faut dire. (Cfr., art. 2.)

2 Comme les combats en l'air, sauf les cas mentionnés dans l'art. b, sont en général interdits on ne pourra tirer sur eux que de cette manière. 3 Comme, en général, dans les mers territoriales des belligérants les vaisseaux neutres ont le droit de libre passage ces mers ne doivent pas être rendues inaccessibles par les dangers de batailles aériennes. Autrement la navigation aérienne, même d'un pays neutre et voisin à un territoire d'un État belligérant pourrait être entravée en grande partie; par example si la France était partie belligérante et l'Angleterre neutre les aérostats anglais seraient, en passant la Manche exposés à des dangers empêchant presque toute la navigation aérienne. Voyez en comparaison, quant à sécurité de la navigation en mer comme en l'air, le projet de M. Fauchille art. 23. It faut prendre en consideration que des courants peuvent très facilement porter les aérostats dans une zone ainsi circonscrite.

ART. 6. Il est interdit aux aérostats privés ennemis de pénétrer dans la sphère aérienne de l'État adversaire.

ART. 7. Les belligérants peuvent interdire aux aérostats neutres de pénétrer dans la sphère aérienne de leur territoire.

ART. 8. Il est interdit de tirer sur des aérostats neutres sans avertissement préalable et de tirer sur eux si, par hasard, ils sont forcés d'atterrir.

Project before the Institute of International Law.The project submitted to the Institute of International Law in 1911, provides:

ART. 22. Les aérostats militaires des belligérants qui pénétrent sur le territoire d'un État neutre ne doivent pas y demeurer plus de 24 heures, à moins que leus avaries ou l'état de l'atmosphere ne les empêchent de partir dans ce délai.

Si des aérostats des deux parties belligérantes se trouvent simultanément en un même point de ce territoire, il doit s'écouler au moins 24 heures entre le départ de l'aérostat d'un belligérant et le départ de l'aérostat de l'autre. L'ordre des départs est detérminé par l'ordre des arrivées, à moins que l'aérostat arrivé le premier ne soit dans le cas où la prolongation de la durée légale de séjour est admise.

Les aérostats belligérants ne doivent rien faire en territoire neutre qui puisse augmenter leur puissance militaire, et leur présence ne doit en aucune manière préjudicier a l'État neutre ; les seuls actes qu'ils peuvent accomplir sont ceux que réclame l'humanité et qui leur sont indispensables pour atteindre le point le plus rapproché de leur pays ou d'un pays allié au leur pendant la guerre.

D'une manière générale, il convient d'appliquer a là guerre aérienne les principes posés par la convention de la Haye du 18 octobre 1907, concernant les droits et les devoirs des puissances neutres en cas de guerre maritime. (24 Annuaire de l'Institute de Droit International, p. 33.)

This project seems to disregard the fact that the character of aircraft is very different from that of craft that keep the sea, as the medium which supports them is also different. More stringent regulations will doubtless be necessary if neutrality is to be maintained and belligerents as to receive treatment to which they are entitled.

Action of institute, 1911.-The Institute of International Law since 1900 have given attention to various. aspects of the regulation of the use of the air. The following vote was adopted at the session of the institute at Madrid in 1911: