This article maps the legally varied sovereignty claims in the contemporary South Pacific; whether secessionist, self-determination based, or consisting of territorial disputes or lesser disagreements. The analysis reveals that Pacific practice in this domain is consistent with general international law; that despite any fractures at the domestic level, relations between the states and territories of the region is peaceful, that their shared values have instead given rise to innovative solutions to legal problems concerning territory, either through the leveraging of regional institutions – so vital to the region’s identity – to pursue claims against metropolitan powers, or through innovative arrangements to alleviate territorial problems left by colonial powers. Indeed, the region is replete with innovative legal solutions based on shared values and peaceful international relations. As such, Pacific practice and engagement with international law can provide a blueprint for others around the globe.

Although evidence shows that territorial disputes fundamentally shape relations among states, we know surprisingly little about when territorial claims are made. We argue that revisionist states have incentives to make territorial claims when the great powers that manage the system are in crisis. We identify five main sources of systemic instability and develop measures of each of them, demonstrating that the majority of territorial claims in Europe are drawn at times when regional great powers are embroiled in crisis, for example, 1848 or 1870 during the nineteenth century. The claims that emerge at these times are not necessarily among states involved in the crises that generated turmoil (e.g., Prussia and France in 1870). We use a newly developed spatial measure of historical boundary precedents in Europe from 1650 to 1790 to demonstrate that the effect of this known spatial correlate of where claims are drawn matters only when the European system is in crisis. We further demonstrate that this claim-timing pattern is general to the global system of states. In the appendix we corroborate our explanation of our findings with a detailed case study of the territorial claims that led to the contemporary Italian state's formation.

In its 2015 judgment in the Costa Rica v Nicaragua case, the International Court of Justice (ICJ) found that Nicaragua's establishment of a military presence in disputed territory violated the territorial sovereignty of Costa Rica. Two judges considered that Nicaragua's actions had constituted a breach of Article 2(4) of the United Nations (UN) Charter, but the majority of the judges chose not to pronounce on the issue. Whilst it has been clarified that the prohibition of the use of force applies to a disputed territory, it seems less clear as to whether such force has to be violent in nature, causing injury to human beings or damage to property, for it to be in breach of Article 2(4). The ICJ's Advisory Opinion on the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory case strongly indicated that the construction of the wall breached Article 2(4). If a State establishes a military presence to change the status quo in a disputed territory, it would not be regarded as a ‘peaceful’ means of settling the territorial dispute. Therefore, such behaviour would violate Article 2(3), under which States shall settle their international disputes ‘exclusively’ by peaceful means. Furthermore, to constitute an unlawful use of force under Article 2(4), the establishment of a military presence in a disputed territory does not have to be violent but should involve coercion that makes it materially impossible for other claimants to restore the status quo ante without risking human injury or damage to property.

The workload of the International Court of Justice in recent years has increasingly featured cases of disputes classified either as ‘territorial disputes’ or as ‘boundary disputes’, or otherwise involving the Court in considerations of the law relating to acquisition or transmission of territory, or to the creation, location and effect of territorial frontiers. The present survey analyzes the contributions to international law of the Court's decisions in these recent cases. Matters examined include the significance of the terms ‘boundary dispute’ or ‘territorial dispute’; the definition of what constitutes sovereign territory; titles and effectivités as bases for territorial claims; decolonization and the uti possidetis juris; use of natural features or of straight lines as boundaries; and relations across a frontier once established.

On November 19, 2012, the International Court of Justice rendered its judgment in a dispute involving territorial and maritime claims raised by Nicaragua against Colombia in the Caribbean Sea. The Court considered Nicaragua’s requests for a declaration of Nicaraguan sovereignty over seven disputed maritime features and delimitation of a single maritime boundary between the continental shelves and exclusive economic zones appertaining to Nicaragua and Colombia. The Court awarded all disputed territory to Colombia and delimited the maritime boundary between the states’ continental shelves and exclusive economic zones by using a novel mix of weighted base points, geodetic lines, parallels of latitude, and enclaving.