Principle in Roman and international law
Uti possidetis is an expression that originated in Roman private law, where it was the name of a procedure about possession of land. Later, by a misleading analogy, it was transferred to international law, where it has had more than one meaning, all concerning sovereign right to territory.
In Rome, if two parties disputed possession of a house or parcel of land, the praetor preferred the one who was in actual occupation, unless he had got it from the other by force, stealth or as a temporary favour ("nec vi, nec clam, nec precario"). The contest was initiated by an interdict called "". The winner was confirmed or restored in possession, and the loser was ordered not to displace him by force. However, the winner had not proved he was the real owner, only that, for the moment, he had a better right to possession than his opponent. Hence the rights of third parties were not prejudiced. The phrase "uti possidetis" was a conventional abbreviation of the praetorial edict dealing with such matters.
In the early modern era, some European states, when dealing with other European states, used the phrase to justify the acquisition of territory by occupation. There was no universally agreed rule and, for example, Portugal applied it more ambitiously than Spain. Despite that, there is no doubt that important polities, such as Brazil, were established on that interpretation. It was also a generally accepted rule about the interpretation of peace treaties. A peace treaty was presumed to give each party a permanent right to the territory it occupied at the conclusion of hostilities, unless the contrary was expressly stipulated. Whether this rule has survived in the international regime following the creation of the United Nations must be doubtful. This usage is sometimes called "uti possidetis de facto."
In recent times, "uti possidetis" refers to a doctrine for drawing international boundaries. When colonial territories achieve independence, or when a polity breaks up (e.g., Yugoslavia), then, in default of a better rule, the old administrative boundaries between the new states ought to be followed. This doctrine, which has its critics, is sometimes called .
Roman law.
Introduction.
A displaced landowner had a theoretically simple way to recover his property: a traditional action called "". All he had to do was to prove he was the owner and the defendant was in possession. However, in reality proof of ownership could be exceedingly difficult for lack of documentation since, during the formative period of Roman law, there was no system of written conveyancing and registration of land. In the Republican era most land transfers were verbal and did not even have to be witnessed. Consequently, as time went by, there must have been many Roman estates whose owners could not prove they were.
Accordingly, in litigation about land each party tried to manoeuvre a situation where the burden of proof was cast on his opponent, and he merely had to defend. To achieve this they went outside the traditional Roman actions and used a praetorial remedy.
Praetorial remedies.
Already in the Roman republic the praetor was an official whose duties included the keeping of the peace. A praetor held office for a year, at the start of which it was customary for him to publish edicts; these announced the legal policies he intended to apply. Usually they were adopted with or without modification by his successors. With these edicts praetors could change the law, though they did it somewhat cautiously.
An interdict was a praetorial order forbidding someone to do something. The one relevant for present purposes was the "interdictum uti possidetis". It seems this interdict was available by about 169 B.C. because there is a joke about it in one of Terence's comedies, though we do not know the praetor's original wording. Probably it originated as a means of protecting occupants of public lands, since these people could not sue as owners. Later, however, it was adapted as a procedural device to assign disputants to the role of plaintiff and defendant, respectively.
The interdict "uti possidetis".
According to the Roman jurist Gaius (Institutes, Fourth Commentary):
A person could establish possession by occupying the property himself, or through another e.g. his "inquilinus" (house tenant) or "colonus" (agricultural tenant).
The three exceptions: "nec vi nec clam nec precario".
That the praetor would confirm the party in possession was only a default rule, since there were three exceptions:
If any of those exceptions applied his possession was flawed (this was called "possessio vitiosa") and did not count.
Third parties.
If he had got his possession from a third party, though, it did not matter that he had done it illegitimately, i.e. it was of no present relevance. This is made explicitly clear by Justinian's Institutes, IV, XV §5: ;templatestyles src="Template:Blockquote/styles.css" / ;He came off victorious who was in possession at the time of the interdict, provided he had not acquired possession as against his adversary by force, or secretly, or at will, although he had expelled "some other person" by force, or had secretly deprived "him" of the possession, or had asked some one ["else"] to allow him to possess at will. ["Emphasis added"] It was up to the third party to initiate legal proceedings about that, if he wanted to; he was not shut out.
This was significant when early modern European powers sought to apply the uti possidetis concept to their colonial acquisitions (see below). Thus, that they had vanquished the indigenous inhabitants by force was of no present consequence if a dispute was between rival Europeans.
Procedure.
On the first appearance in court the praetor, whose time was valuable, did not try to investigate the facts. He simply pronounced the interdict impartially against both parties. (Hence it was called a "double interdict"). Conceivably, one of the parties knew he was in the wrong and decided he had better obey the praetor's interdict. If so, that was the end of the matter. Suppose, however, he chose to brazen it out or, indeed, sincerely believed himself to be in the right.
The next step was to bring matters to a head. Accordingly, on a prearranged day the parties would commit a symbolic act of violence ("vis ex conventu") e.g. pretending to expel each other from the land. That, for the one in the wrong, must have been a formal disobedience of the praetor's order. Each party now challenged the other to a wager by which he had to pay his adversary a sum of money if it was he who had disobeyed the interdict. (This way of settling disputes in Rome — by having a wager on the result — was called "agere per sponsione"). The "agere per sponsonie" was sent off to be tried by a "iudex" (akin to a one-man jury, usually a prominent citizen), who in due course delivered his decision. Meanwhile, the right to interim possession of the land was auctioned to whichever of the two contestants was the highest bidder, on his promise to pay his adversary the rent if he turned out to be in the wrong.
Roman litigation was not for the faint-hearted. Getting one's opponent into court at all could be difficult, and arguably praetors "were nothing more than politicians, frequently incompetent, open to bribery, and largely insulated against suits for malfeasance". A litigant could frustrate the interdict process by omitting to take part in its rituals. When that happened, however, it was possible to obtain a secondary interdict by which he lost the case at once.
Advantages of the interdict.
Although the interdict neither conferred nor recognised any proprietary right, the party who prevailed had achieved three important advantages.
First, he enjoyed peaceful possession of the land against his adversary for the time being. Secondly, although his opponent might yet get the land — by bringing a "vindicatio" — the case had to be proved. This was important since it assigned the burden of proof. Thirdly, and in practice, his opponent might not trouble to take it further. Then, the party left in possession looked very like the real owner. As time went by it must have become more and more difficult to prove he was not.
In sum, by peaceful, open and unlicensed possession of land a party did not acquire ownership, but he did acquire practical advantages.
The Roman doctrine about establishing possession (not ownership) may seem slightly elusive for those brought up in the Anglophone common law where it is trivially obvious that a good title to land can indeed be acquired by mere occupation (e.g. "squatters' rights"). However, it was not so in Roman law which drew a sharp line between ownership and possession. Except in special cases, mere occupation of land could not confer ownership.
Later knowledge: the text of the edict.
Although Gaius' text was imperfectly known to early modern Europeans, because it was lost and not rediscovered until 1816, they knew the edict in the later recension by Justinian. The interdict's name "uti possidetis" was a conventional abbreviation of the wording of the praetorial edict: ;templatestyles src="Template:Blockquote/styles.css" / ;Uti eas aedes, quibus de agitur, nec vi nec clam nec precario alter ab altero possidetis, quo minus ita possideatis, vim fieri veto. De cloacis hoc interdictum non dabo: neque pluris quam quanti res elit; intra annum, quo primum experiundi potestas fuerit, agere permittan. (Dig. 43, 17, 1)
which has been translated ;templatestyles src="Template:Blockquote/styles.css" / ;Whichever party has possession of the house in question, without having acquired it either by violence, or clandestinely, or by leave and licence of the adversary, the violent disturbance of his possession I prohibit. Sewers are not included in this interdict. The value of the thing in dispute and no more may be recovered, and I will not allow a party to proceed in this way except within the first year of days available for procedure ("annus utilis").
Much later, when it came to be adopted in international law the abbreviation was represented as "Uti possidetis, ita possideatis" ("as you possess, so may you possess"), whereby "possession became ten-tenths of the law", said to be a perversion of the Roman doctrine.
"Uti possidetis" as a doctrine for the acquisition of territory in international law.
From Roman private law, uti possidetis was transposed to international law as an assertion of sovereignty over territory, although the analogy was misleading.
European powers, when they sought to justify their acquisition of territory in America and elsewhere, based their claims on a variety of legal concepts. One argument was that the new lands were "terra nullius" (belonging to nobody) and so could be acquired by occupation. But some prominent European jurists and theologians, like Francisco de Vitoria, rejected this, arguing that the lands did have owners: the indigenous peoples. However, since the European powers were not seeking to justify themselves to the indigenous people, but to their European rivals, all they needed to show was a better claim, not an absolute one. Here they found the Roman law uti possidetis analogy valuable.
Apparently it was first devised by the Portuguese diplomat Luís da Cunha in order to justify his country's claims to territory in colonial South America, though some have attributed the idea to the Luso-Brazilian diplomat Alexandre de Gusmão.
While Spanish-American states may have been content to draw mutual boundaries by adopting the internal administrative divisions of the old Spanish Empire (see "uti possidetis juris", below), this was not done as between Portuguese-America (Brazil) and the Spanish-American polities, and was not possible. Explained John Bassett Moore: ;templatestyles src="Template:Blockquote/styles.css" / ;There can be no more conclusive proof of the futility of the attempts made by Portugal and Spain to fix the limits of their dominions in South America than the fact that they left to their successors no treaty by which those limits purported to be determined.
The Brazilian frontier movement into Spanish-claimed lands.
In 1494 Spain and Portugal agreed to modify the 1492 papal bull which divided the world into two spheres of influence, with each country agreeing that it would respect the other's acquisitions on either side of an imaginary line. The Treaty of Tordesillas modified this imaginary line running from pole to pole: Spain was to have the lands to the west of that line, Portugal to the east. Shortly afterwards, and around the same time, expeditions from both countries discovered South America. As the new continent was explored it was gradually realised that the Tordesillas line, though rather vague, gave Portugal only a corner of