[§ 47. Method of Acquisition]
The method of acquisition of territorial jurisdiction is a subject which has received much attention in international law, particularly because of the remarkable expansion of the territorial area of states within the modern period of international law since 1648.
The methods commonly considered are: (1) discovery, (2) occupation, (3) conquest, (4) cession, (5) prescription, (6) accretion.
(a) In the early period of European expansion through discovery, the doctrine that title to land hitherto unknown vested in the state whose subject discovered the land was current. Gross abuse of this doctrine led to the modification that discovery without occupation did not constitute a valid title. As the field of discovery has grown less, the importance of a definition of occupation has decreased.
(b) Occupation is held to begin at the time of effective application of state authority, and strictly continues only during the exercise of such authority. In fact, however, the title by occupation is held to extend to the adjacent unoccupied territory to which the state might potentially extend the exercise of its authority, or where it may from time to time exercise its authority in an undisputed manner. Title by occupation extends as a rule to that area, not under the jurisdiction of another state, which is necessary for the safety of the occupied area or is naturally dependent upon it, as to the territory drained by a river of which a given state holds the mouth.
The "Hinterland Doctrine," brought forth during the latter years of the nineteenth century, advances the idea that no such limits as above shall bound the area which can be claimed on ground of occupation, but that coast settlements give a prima facie title to the unexplored interior.
While the uncivilized peoples living within an area to which a civilized state claimed jurisdiction by virtue of occupancy were often unjustly treated, they however "were admitted to be the rightful occupants of the soil, with a legal as well as just claim to retain possession of it, and to use it according to their own discretion, though not to dispose of the soil of their own will, except to the government claiming the right of preëmption.... The United States adopted the same principle, and their exclusive right to extinguish the Indian title by purchase or conquest, and to grant the soil, and exercise such a degree of sovereignty as circumstances required, has never been questioned."[126]
(c) Conquest in the technical sense of the status of a territory which has come permanently under the jurisdiction of the enemy is distinct from military occupation, which is a simple fact supported by force.
Military occupation may pass into conquest (1) by actual occupation for a long period, with intention on the part of the occupier to continue the possession for an indefinite period, provided there has not been a continued and material effort upon the part of the former holder to regain possession. If, after a reasonable time, this effort to regain possession seems futile, the conquest may be regarded as complete. Each state must judge for itself as to the reasonableness of the time and futility of the effort. (2) Conquest may be said to be complete when by decree, to which the inhabitants acquiesce, a subjugated territory is incorporated under a new state. (3) A treaty of peace or act of cession may confirm the title by conquest.[127]
(d) Transfer of territory by cession may be by gift, exchange, or sale.