Uti possidetis

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 uti possidetis. 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 uti possidetis juris.

A displaced landowner who wanted to recover his property could bring a traditional action called vindicatio, which was theoretically a simple procedure. All he had to do was to prove he was the owner and the defendant was in possession. But 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.

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 if expelled could not have sued as owners. Later, however, it was adapted as a procedural device to assign disputants to the role of plaintiff and defendant, respectively.