There were a variety of theories prior to the First World War with regard to the status of the airspace above states and territorial waters. One view was that the airspace was entirely free, another that there was, upon an analogy with the territorial sea, a band of territorial air appertaining to the state followed by a higher free zone, a third approach was that all the airspace above a state was entirely within its sovereignty, while a fourth view modified the third approach by positing a right of innocent passage through the air space for foreign civil aircraft.

There was a particular antagonism between the French theory of freedom of the air and the British theory of the state sovereignty, although all agreed that the airspace above the high seas and terrae nullius was free and open to all.[i]

Explanation
However, the outbreak of the First World War, with its recognition of the security implications of the use of the air, changed this. Efforts to ascertain the breadth of the layer of air comprised within the air territory so as to establish a consensus and acceptable principle of sovereignty over the air space had generated a lot of controversy amongst jurists.

This controversy had given rise to theories propounded on a stage by stage basis which subsequently led to the birth of the principle of sovereignty over the air space. The theories of sovereignty over the air space propounded by the jurists were initially grouped into two main schools of thought. These are the theory which maintained that the air space is by its nature free and that which maintained the theory of sovereignty of the subjacent state in the airspace above its territory.

The theories on the legal status of the airspace may be summarized as follows:

1. Theory Of The Unlimited Freedom

   This theory is supported by those who, having seen the advantages that the absolute freedom of the seas have brought to the International community, thought that the same criteria could be applied to the air navigation.
   
   The theory is criticized on the ground that it is contrary to many international treaties. Each state exercises control over its airspace and the aircraft of another state can enter its airspace only after seeking its prior permission.
    

2. Theory of Absolute Sovereignty

   This theory is completely opposed to the previous one; it refused the principle of freedom, and conversely claimed State sovereignty over the atmosphere. It also inherited the idea that the Roman law had applied to the land property in order to define its unconditional character and to reject any claim from the other States.
   
   The theory is criticized the ground that in view of the rapid scientific and technological developments, aircraft can go to a very high altitude. It is not possible for each State to exercise control over unlimited height.
    

3. Intermediate Theories

   It tried to combine the States' claims with the creation of an efficient International air navigation system. One of the most famous theories were formulated in 1901 by the French jurist Paul Fauchille, who claimed that the air is free, and its freedom may only be limited by strictly defined rights belonging to the State underneath. Accordingly, the sovereignty of the landowner over the air space was limited to the maximum height of the buildings it could build; beyond this limit, the atmosphere was free and freely exploitable. The greatest difficulty in accepting this theory is that no State is prepared to accept it affirmatively.
    

4. Theory Of The Limited Sovereignty

   It stemmed from the principle that the atmosphere is subject to the State power, but it introduced some limitations in favor of the air traffic of adequate means whose airworthiness could be proved by specific international certifications. This theory anticipated the following regime which was based upon a functional and not just the spatial idea of air navigation.

Again this theory was not acceptable to many States as the concept of limited sovereignty was considered as a significant compromise on the idea of absolute sovereignty.

The Principle of Sovereignty over the Airspace

• I see no good reason for postponing a systematic effort to explore and reach agreement on this question of delimiting the upward reach of territorial sovereignty, that is, the exclusive power and authority of the underlying state. It is not the kind of question, in my opinion, that will be answered by the accumulation of scientific knowledge or by further experience in space technology. [ii]
   
• State sovereignty over its territorial airspace is the basic principle underlying the whole system of International Air Law. Irrespective of whether the airspace can be regarded as a part of a state's territory, it generally recognized that it is a sovereign right over the airspace above its land and territorial waters. After the collapse of the short-lived concept of freedom of the air in the first decade of the 19th century, air law theory is based on the concept of air sovereignty as airspace is regarded as an extension of the state's land and maritime territorial or its complementary element. [iii]
   
• States have exercised sovereignty over the space above the land at least as far back as the Roman Empire. Roman law (and the law of succeeding States) recognized, regulated, and protected privacy rights in space above the surface. [iv]
   
• Air Law applies to airspace and aircraft. States enjoy “complete and exclusive sovereignty” over their territorial air space. The Convention on International Civil Aviation (also known as Chicago Convention) states that “Every the state has complete and exclusive sovereignty in the airspace above its territory”. [v]
  
  It also declares that:
  “Territory includes the land areas and territorial waters adjacent thereto”. Air Law imposes liability on the airline, or the aircraft operator and requires States to certify and register aircraft, and environmental standards. Air Law requires States to regulate safety, navigation, and security; it also States requires to regulate noise and emissions.
   
• Article 3 adds that:
  No state aircraft of a contracting State shall fly over the territory of another State or land thereon without authorization by special agreement or otherwise, and in accordance with terms thereof”[vi]
   
• Article 6 that:
  A State‟s territorial airspace includes the area above its territorial waters, there exists no right of innocent passage and scheduled international air services are only allowed with special permission of the contracting States”[vii].
   
•  Accordingly, international law rules protecting the sovereignty of states apply to the airspace as they do to the land below. As the International Court noted in the Nicaragua case, ‘the principle of respect for territorial sovereignty is also directly infringed by the unauthorized Overflight of a state's territory by aircraft belonging to or under the control of the government of another state.'[viii]
   
• The Court noted in the Benin/Niger case that‘a boundary represents the line of separation between areas of state sovereignty, not only on the earth's surface but also in the subsoil and in the superjacent column of air'.[ix]

Problems of National Jurisdictions regarding Airspace Sovereignty

There is no system of general rules of international law for the definition of the scope of national laws and jurisdictions. In the view of the basic rules of international law recognizing complete and exclusive sovereignty of states over state-territorial airspace involving the prohibition of unauthorized flights and obligation to conform to territorial laws and regulations by the foreign aircraft, the implementation of these rules by the state becomes most important.

As experienced, international law does not provide an immediate measure to protect territorial airspace and to cease the violation. The mentioned „freedom of the air‟, like the „sovereignty‟ itself in the basic rule of international law, cannot be considered solely to be absolute and unrestricted.

State sovereignty in territorial airspace and its legal consequences cover:

1. Freedom of air navigation in non-territorial airspace;
2. Nationality of aircraft involving control, responsibility;
3. Right of protection assigned to the registered state [x] of the flag;
4. Use of lawful means to suppress unlawful use of aircraft;
5. Recognition either of exclusive jurisdiction of the territorial state or of state of the aircraft's nationality; and
6. Concurrent jurisdictions in other areas of civil aviation activities.

Conclusion

• There is no right of innocent passage through the airspace of a state. Aircraft may only traverse the airspace of states with the agreement of those states, and where that has not been obtained an illegal intrusion will be involved which will justify interception, though not (save in very exceptional cases) actual attack.
  
  However, the principle of the complete sovereignty of the subjacent state is qualified not only by the various multilateral and bilateral conventions which permit airliners to cross and land in the territories of the contracting states under-recognized conditions and in the light of the accepted regulations but also by the development of the law of outer space.
   
• Even if these treaties are not binding on some states, because they are not parties to them, these rules also fall under the provisions of customary international law, and as such, are binding on all states, breach of which constitutes a violation of international law.

End-Notes:

1. Shaw, M. (2003). Air law and space law. In International Law (pp. 463-489). Cambridge: Cambridge University Press. DOI:10.1017/CBO9781139051903.011
2. The Honorable John A. Johnson, First General Counsel of the U.S. National Aeronautics and Space Administration, 1961
3. Tang Ut Fong, Air Law.
4. John Cobb Cooper, Roman Law and the Maxim “Cujus est solum” in International Air Law, reprinted in JOHN Cobb Cooper, Explorations In Aerospace Law 54, 57 – 58 (Ivan A. Vlasic, ed., 1968)
5. Article 1 of Chicago convention (The 1944 Convention on International Civil Aviation)
6. Article 3 of Chicago convention (The 1944 Convention on International Civil Aviation)
7. Article 6 of Chicago convention (The 1944 Convention on International Civil Aviation)
8. ICJ Reports, 1986, pp. 14, 128; ILR, p. 176 ILR, p. 1
9. ICJ Reports, 2005, p. 142
10. Art 1(2) of the Tokyo Convention stating that „this convention shall apply in respect of offenses committed or acts done by a person on board any aircraft registered in a contracting state, while that aircraft is in flight or on the surface of the high seas or of any other area outside the territory of any state.

Written By: Sandeep Rana, BA+LLB (Hons) student at Chandigarh University, Gharuan.