The present article aims to examine a set of legal constructions related to the concept of legal title in territorial disputes. Any international jurist cannot but strongly feel the need of a theoretical approach and framework explaining the acquisition and loss of territorial sovereignty. This conceptualization will be put to the test in the light of the ICI's case law, especially, but not exclusively, the most recent ones. To this end, the article is structured in three main parts in addition to introduction: the first will be devoted to the building of a comprehensive concept of territorial title while rejecting the traditional ‘modes of acquisition’ of territorial sovereignty (part 2). Part 3 will deal with the legal processes through which territorial titles are actually created, extinguished, or modified: roughly speaking, this happens by an international agreements (legal acts) or by virtue of norm-creating facts. Last, but not least, we shall examine – in part 4 – the highly debated and sensitive topic of the relations between effectiveness and formal legal title from the standpoint of the establishment or loss of territorial sovereignty. As we have endeavoured to show in this writing the concept of legal title reunites and resolves the tension between fact (effectiveness) and formal gegal title (law). In this respect four situations will be put under scrutiny in order ultimately to test our construction of a new concept of territorial title.