The Article explores the history and development of uti possidetis juris to see how it has been applied to previous disputes about states emerging from Mandatory territories, which are neither “classic decolonizations” nor the breakup of composite states. . . . We find that that uti possidetis juris has been fully applied to the numerous border disputes regarding former Mandatory territories, notwithstanding Mandates’ odd juridical status — they were neither full-pledged state, nor a mere colonial possession, nor an administrative unit of the Mandatory power. We find that bitter controversies about the borders of the Palestine Mandate are far from particular to Palestine. Similar controversies emerged regarding the borders of many other Mandates, because they often took little account of national self-determination interests, and were in several instances illegally modified by the Mandatory. Numerous Mandates were plagued by international doubts about their wisdom of their borders and serious discussions of revision. Yet in all cases, the borders of the Mandate as they stood at independence became the borders of the new successor state.

* * *

At its expiration in 1948, the borders of the Mandate of Palestine, both internal and external, were relatively well demarcated and uncontroversial. Thus uti possidetis juris could be a powerful tool for resolving extant disputes about the borders of Israel. To be sure, Israel appears to be interested in drawing consensual new boundaries that differ from the borders established by uti possidetis juris. Uti possidetis juris does not preclude later modifications of borders. Application of uti possidetis juris, as is customary in other boundary disputes, would nevertheless provide a clear baseline for future negotiated solutions.