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Max Planck Encyclopedia of Public International Law [MPEPIL]

Uti possidetis Doctrine

Giuseppe Nesi

Self-determination — Foreign relations law — Sovereignty — Settlement of disputes — Boundaries — Territory, acquisition and transfer

Published under the auspices of the Max Planck Foundation for International Peace and the Rule of Law under the direction of Rüdiger Wolfrum.

A. Notion and Historical Development

The expression uti possidetis originates in Roman law, where it indicated an interdict by the praetor aimed at prohibiting any interference with the possession of immovable property acquired nec vi, nec clam, nec praecario (not by force, nor stealth, nor license). The purpose of uti possidetis was to temporarily assign a favourable position in the ownership action to the individual who possessed that property.

In the context of the international law of war, uti possidetis initially (in the 17th century) described the situation on the ground after an armed conflict (see also Armed Conflict, International). The right to territory acquired through conflict was de facto consolidated by making recourse to a misleading analogy with the uti possidetis doctrine in the Roman era. This notion of uti possidetis is no longer viable since the well-established principles on the use of force do not allow for any acquisition of territory that is in violation of the United Nations Charter (145 BSP 805) (see also Territory, Acquisition).

The modern meaning of uti possidetis in international law dates from early 19th century Latin America (Boundary Disputes in Latin America). In Latin America, uti possidetis, and more precisely uti possidetis iuris, was qualified as a regional norm for the determination of boundaries. Through uti possidetis iuris the newly decolonized States felt bound to adopt as their international boundaries the delimitations—usually administrative but sometimes international in character—traced or tolerated by the colonial authorities and existing at the date of independence, thus contributing to the consolidation of the norm. The Brazilian concept of uti possidetis de facto emphasized instead the de facto situation at the time of independence, but it was confined to Brazil. At this point in time, in Latin America uti possidetis iuris was deemed to be: (i) a sui generis instrument covering the succession of new States to colonial powers; (ii) a derogation to effectiveness as a condition for acquiring territorial sovereignty; (iii) a means of promoting the defence of the continent against further colonization attempts; (iv) a principle concerning the determination of boundaries between States arising from the decolonization process. The relevance of the principle to territorial delimitation was crucial in inter-American relations, as inter-State practice and judicial and arbitral decisions demonstrate.

Until the mid-20th century, it was rare to find references to this principle outside of Latin America. In the 1960s it appeared in Africa to describe borders between States born from decolonization (Boundary Disputes in Africa). At the end of the colonial period some African leaders envisaged an ideal Pan-Africanism that could have solved the problem of territorial delimitations among the newly constituted States. However, the doctrine of national States prevailed, obliging the African Heads of State and Government to single out which rule should be applied to those delimitations. Thus, in Africa uti possidetis appears as a norm that determines the boundaries between decolonized States on the basis of territorial, administrative, or international divisions established during colonial rule. This interpretation can be deduced from solemn declarations by African States; the Organization of African Union Cairo Resolution of 1964 (OAU ‘Border Disputes among African States’ AHG/Res.16[I] [17–21 July 1964]; ‘1964 OAU Cairo Resolution’); several delimitation agreements; many arbitral compromises deferring the settlement of territorial disputes to the International Court of Justice (ICJ) and arbitral tribunals; some international judicial and arbitral decisions (Frontier Dispute Case [Burkina Faso/Republic of Mali]; Land and Maritime Boundary between Cameroon and Nigeria Case [Cameroon v Nigeria]; Maritime Boundary between Guinea and Guinea-Bissau Arbitration [Guinea v Guinea-Bissau]; Frontier Dispute Case [Benin/Niger]).

One could wonder whether the Latin American uti possidetis differs from the uti possidetis applied in Africa, as was the case for the Arbitral Tribunal dealing with the dispute between Senegal and Guinea-Bissau (Arbitral Award [31 July 1989]; Maritime Boundary between Guinea-Bissau and Senegal Arbitration and Case [Guinea-Bissau v Senegal]). On that occasion the Tribunal stated that the Latin American uti possidetis would refer only to intracolonial territorial divisions, while in Africa the principle would apply to territorial divisions set up both by a colonial authority within its territory and by different colonial powers (see also Colonialism). This attempt to distinguish an ‘African’ uti possidetis was criticized as completely ‘unfounded’ by one of the arbitrators. In light of this criticism, one must recognize how uti possidetis was largely applied in Latin America in relationships among countries previously under Spanish colonial domination only because the greatest part of that continent was under Spanish sovereignty. Nevertheless, in territorial disputes involving Brazil, which was under Portuguese colonial domination, or European colonial powers (the United Kingdom and the Netherlands, for instance) uti possidetis was also referred to as a fundamental norm to be applied in territorial delimitations in Latin America.

The relevance of uti possidetis in various decolonization contexts outside of Africa (Temple of Preah Vihear Case; Rann of Kutch Arbitration [Indo-Pakistan Western Boundary]) and in non-decolonization contexts (eg, the dissolution of federal States) has been confirmed in recent years (Yugoslavia, Dissolution of). In the territory of the former Union of Soviet Socialist Republics (USSR) the international borders between the new States coincided with the borders between the former federated Republics.

The historic evolution of uti possidetis demonstrates that it is a norm of international law governing territorial delimitations. Uti possidetis is not a peremptory norm of international law, since States can derogate from it by common consent, as was often the case in both Latin America and Africa. In other words, uti possidetis is perceived as the basis of delimitation between newly constituted States until and unless those States decide to adopt different boundaries.

In recent times international jurisprudence has debated the relevance of uti possidetis in maritime delimitations (Maritime Delimitation Cases before International Courts and Tribunals; Arbitral Award of 31 July 1989 (Guinea-Bissau v Senegal); Land, Island and Maritime Frontier Dispute Case [El Salvador/Honduras: Nicaragua Intervening]; Maritime Delimitation between Nicaragua and Honduras in the Caribbean Sea Case [Nicaragua v Honduras]). Divergent views have emerged on this issue among those who denied any relevance to the principle because of the different features of territorial and maritime delimitations; others, on the contrary, were in favour of the relevance of uti possidetis in maritime delimitations because in both maritime and territorial delimitations uti possidetis aims at ensuring the stable and final character of existing boundaries. The latter position presupposes, as it happens for the application of uti possidetis in any circumstance, the fact that delimitations were already in place. And when, more recently, the ICJ decided not to apply uti possidetis to maritime delimitations (Territorial and Maritime Dispute [Nicaragua v Colombia] [2012] ICJ Rep 624), it did so not because uti possidetis was not deemed relevant but because the parties failed to adequately support their claims:

the Court concludes that in the present case the principle of uti possidetis juris affords inadequate assistance in determining sovereignty over the maritime features in dispute between Nicaragua and Colombia because nothing clearly indicates whether these features were attributed to the colonial provinces of Nicaragua or of Colombia prior to or upon independence. The Court accordingly finds that neither Nicaragua nor Colombia has established that it had title to the disputed maritime features by virtue of uti possidetis juris (at para. 65).

The norm aims to avoid disputes over territorial delimitations. In this respect, the uti possidetis doctrine arguably meets two needs: it prevents boundary disputes, and it deters the local exploitation of weaknesses and disorders in newly created States which are often vulnerable to secessionist actions (Secession). The first need corresponded to Latin America, while both clearly corresponded to Africa and other parts of the world in recent times. Uti possidetis is today a norm of customary international law, which does not have constitutive effect and can be derogated consensually by the States involved, invoked to determine the boundaries in newly independent States wherever they may be, thus also in contexts other than decolonization (see paras 11–23 below).

10 In this regard, uti possidetis contributes to stability in international relations. In its ultimate aims, it is similar to the principle of intangibility of frontiers enshrined in the 1964 OAU Cairo Resolution, although the latter refers to the prohibition of the use of force against territorial integrity and political independence (as provided by Art. 2(4) UN Charter), while uti possidetis is instrumental to the determination of boundaries between newly independent States.

B. Application

11 The first aspect of the application of uti possidetis iuris to be considered is the ‘critical date’, ie, the historic moment when the delimitation is made by taking ‘a photograph of the territory’. The issue of the critical date is intertwined with that of the elements for applying uti possidetis: are there only formal elements or also informal elements? By ‘formal elements’ one alludes to all the formal acts issued in the colonial (or pre-independence) era indicating the existence in that period of a delimitation in a certain area. For example, laws and regulations issued by the former sovereign and describing the limits between various administrative entities. Informal elements amount rather to conduct (or acquiescence) of the previous sovereign. Acts adopted and conduct taken prior to independence have a paramount role in determining boundaries according to uti possidetis. Uti possidetis is in principle based on the legal acts (‘titles’) adopted by the former sovereign before independence, and on the legal relationship between those acts and the effectivités (ie, ‘the conduct of the administrative authorities proving the effective exercise of territorial jurisdiction in the region during the colonial period’ [Frontier Dispute Case (Burkina Faso/Republic of Mali) at para. 63]). Frequently the reference parameters were widened: when this happened, both formal elements and conduct from which the existence of territorial divisions at the critical date could be inferred were taken into consideration.

12 According to the Chamber of the ICJ in the Frontier Dispute Case (Burkina Faso/Republic of Mali), there can be several scenarios with regard to the way effectivités interact with titles:

Where the act corresponds exactly to law, where effective administration is additional to the uti possidetis juris, the only role of effectivités is to confirm the exercise of the right derived from a legal title. Where the act does not correspond to the law, where the territory which is the subject of the dispute is effectively administered by a State other than the one possessing the legal title, preference should be given to the holder of the title. In the event that the effectivité does not co-exist with any legal title, it must invariably be taken into consideration. Finally, there are cases where the legal title is not capable of showing exactly the territorial expanse to which it relates. The effectivités can then play an essential role in showing how the title is interpreted in practice (at para. 63).

It is thus evident for the ICJ Chamber that the legal title has primary relevance in the application of uti possidetis, although effectivités become decisive if legal titles are not available or their interpretation is difficult.

13 Acts issued during the period subsequent to the critical date and other data related to that period, including the conduct of States towards unequivocal claims by others, can be taken into consideration as useful elements in obtaining a clearer picture of the situation on the ground at the critical date. In this respect it has been recently stated by the ICJ that, after a perusal of the acts issued by Colombia in a certain area claimed also by Nicaragua and the lack of reaction of the latter (Territorial and Maritime Dispute [Nicaragua v Colombia] [2012] ICJ Rep 624):

It has thus been established that for many decades Colombia continuously and consistently acted à titre de souverain in respect of the maritime features in dispute. This exercise of sovereign authority was public and there is no evidence that it met with any protest from Nicaragua prior to the critical date. Moreover, the evidence of Colombia’s acts of administration with respect to the islands is in contrast to the absence of any evidence of acts à titre de souverain on the part of Nicaragua. The Court concludes that the facts reviewed above provide very strong support for Colombia’s claim of sovereignty over the maritime features in dispute (at para. 84).

14 If a delimitation treaty is concluded after independence, uti possidetis does not apply (Territorial Dispute Case [Libyan Arab Jamahiriya/Chad]) because the agreed delimitation overrides the pre-existent uti possidetis, although the former could also coincide with the latter.

15 According to the ICJ in the Land and Maritime Boundary between Cameroon and Nigeria (Cameroon v Nigeria: Equatorial Guinea Intervening) ([2002] ICJ Rep 303), even if uti possidetis is applicable, a consolidated acquiescence can overcome the former.

16 A review of the practice also indicates that, when particular difficulties in the application of uti possidetis iuris arise, equitable criteria are often considered. In these cases, equity has integrated uti possidetis iuris (equity infra legem) but has not substituted the principle (see also Equity in International Law). This is the position of the ICJ Chamber in the Frontier Dispute Case (Burkina Faso/Republic of Mali), according to which the equity to be applied in the specific case is not equity contra or praeter legem; it is rather ‘equity infra legem, that is, that form of equity which constitutes a method of interpretation of the law in force, and is one of its attributes’ (at para. 28). And it further specifies that ‘[h]ow in practice the Chamber will approach recourse to this kind of equity in the present case will emerge from its application throughout this Judgment of the principles and rules which it finds to be applicable’ (ibid). However, equity infra legem is applied with great caution:

The Chamber would however stress more generally that to resort to the concept of equity in order to modify an established frontier would be quite unjustified. Especially in the African context, the obvious deficiencies of many frontiers inherited from colonization, from the ethnic, geographical or administrative standpoint, cannot support an assertion that the modification of these frontiers is necessary or justifiable on the ground of considerations of equity. These frontiers, however unsatisfactory they may be, possess the authority of the uti possidetis and are thus fully in conformity with contemporary international law (at para. 149).

17 In recent years the applicability of uti possidetis in situations other than decolonization has also been debated in Europe, where the conclusion was drawn that it is applicable provided that a delimitation exists at the critical date. Recent events such as the dissolution of the Soviet Union, Yugoslavia, and Czechoslovakia confirm this interpretation (Czechoslovakia, Dissolution of). Reference to uti possidetis iuris was first made with regard to Yugoslavia. The Badinter Commission (for the Former Yugoslavia) took a stand in favour of the maintenance of the administrative borders that divided one federated Republic from the other until dissolution took place. According to Opinion No 3 ([11 January 1992] [1992] 3 EJIL 184) of the Badinter Commission, those administrative frontiers would become international boundaries because of uti possidetis iuris, unless the parties agreed otherwise.

18 The Badinter Commission’s conclusion was contested by some scholars, although it was applied for the international frontiers of the former Yugoslavia and the transformation of the administrative divisions between the former federated Republics into international boundaries. Specific attention should be given to the fact that all the proposals by international negotiators seeking a peaceful solution in the area were initially based on the territorial divisions on the date of independence of the new entities. This fact was undisputed by the parties. In one of the most contested areas, Bosnia and Herzegovina, the proposed international delimitation of the new State coincided in its entirety with the delimitation that constituted the border of the former federated Yugoslav Republic of Bosnia and Herzegovina on the date of independence. Against this background, the acceptance of uti possidetis was interpreted as a necessary preliminary phase in which the parties decided, by mutual consent, which territorial modifications had to be made. This is confirmed by the content of Annex 2 to the Dayton Agreement (General Framework Agreement for Peace in Bosnia and Herzegovina [signed and entered into force 14 December 1995] (1996) 35 ILM 89). Observations similar to those made on the Federal Republic of Yugoslavia can be made, mutatis mutandis, for the dissolution of the USSR and Czechoslovakia. In the former case, the boundaries of the former 15 Republics coincided with those of the new States. In the latter, the international boundary set in 1993 coincided with the delimitation separating the two federated entities between 1918 and 1992 and with the international boundary in force between Austria and Hungary before 1918.

19 Uti possidetis can be applied to boundaries which were either internal (intra-colonial or between federated Republics) or international during the colonial or federal period. The exact location of frontier lines is often referred to—especially in cases of internal boundaries before independence—in specific agreements or in arbitral awards. Those States where uti possidetis has been most frequently applied, ie, Latin America and African States, deemed uti possidetis as a starting point when drafting specific delimitation agreements or deferring the issue of boundary determination to an arbitrator.

20 Uti possidetis is a norm operating particularly in the first phase of the relationships established between newly independent States. Unless there are other points of reference, these States adopt pre-existing delimitations as international frontiers. With the passage of time uti possidetis as the norm autonomously defining the territory of newly independent States is ‘overridden’ (rectius ‘specified’) by the delimitations set by these very States. In this context, uti possidetis tends to act as a norm that ‘retires’ when two neighbour States set their boundaries either by agreement or arbitral decision. Thus, in contemporary international law uti possidetis applies only when delimitations set before independence are identified or when a ‘new’ delimitation has not been drawn on the basis of other principles or criteria.

21 A final aspect of the functioning of uti possidetis refers to its relationship to the right of people to self-determination. Those who believe that there is a conflict between uti possidetis and self-determination underline the arbitrary nature or authoritarian character of delimitations of the colonial era or of the central authorities of a federal State against the will of the interested populations. In Frontier Dispute (Burkina Faso/Republic of Mali) it was stated that, ‘at first sight’ uti possidetis ‘conflicts outright’ with the right of people to self-determination (at para. 25). In the same case it was said, however, that the maintenance of the status quo in Africa is

[O]ften seen as the wisest course, to preserve what has been achieved by people who have struggled for their independence, and to avoid a disruption which would deprive the continent of the gains achieved by much sacrifice (at para. 25).

According to a synthetic and enlightening statement of a former President of the ICJ, Dame Rosalyn Higgins, ‘[u]ti possidetis does not prevent States freely agreeing to redraw their frontiers. But self-determination does not require this of them.’

22 If one sees uti possidetis as a norm for determining boundaries between newly constituted States, a conflict between the two principles can be envisioned only if, during colonial times, territorial delimitations had the sole purpose of dividing homogeneous populations or ethnic or religious groups. If this is the case, the violation of the right of people to self-determination is so blatant that those delimitations can be qualified as illicit acts. Some authors underline that we should not underestimate the consequences of adopting territorial delimitations which, on certain occasions, ignore the century-old ethnic, social, and cultural fabric of the territory; however, it was also observed that framing an inevitable conflict between the two principles in such cases means assigning an inappropriate role to uti possidetis. In fact, the two principles have different functions: uti possidetis refers to territorial delimitations of newly independent States, while the right of peoples to self-determination concerns the freedom of a people to choose its political, economic, and social status.

23 According to some scholars, it is not always necessary to draw ex novo international frontiers to allow people living in a territory belonging to a newly independent State to exercise their right of self-determination. The right of a people to self-determination can be achieved through means other than redrawing the delimitations existing at the time of independence: for example, when newly independent States have agreed upon territorial modifications and the population concerned has been authorized to vote thereon, or where there is transborder cooperation. History teaches that when uti possidetis is contested by one party and no alternative to uti possidetis is provided (such as the conclusion of a delimitation agreement or the deferral of the delimitation to a judicial or arbitral award) the risk of instability and clashes increases enormously.

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