Even the casual observer of international affairs can appreciate the significance of prohibiting states from forcibly taking the territory of other states. The modern international order is structured around a stable set of territorially defined states, which have remained remarkably free from forcible territorial changes since World War II, a dramatic departure from the preceding era.
The prohibition has historically been maintained by U.S. security commitments, which are currently at great risk from President Trump’s threats against Palestine, Canada, and Denmark; Russia’s attempts to annex parts of Ukraine; Israel’s efforts to annex parts of the West Bank and the Golan Heights; as well as events in Nagorno-Karabakh, the South China Sea, the Western Sahara, and elsewhere.
In their article “The Prohibition of Annexations and The Foundations of Modern International Law,” Ingrid Brunk and Monica Hakimi argue that the international legal norm that lies at the core of this change—the prohibition of annexations—is foundational to contemporary international law. They also explain how its origins and doctrinal status are shrouded in confusion, and that there is good reason to believe that today, it is at serious, under-appreciated risk of erosion.
The prohibition, as the article explains, is intricately connected to three central projects in international law.
The first works to establish and entrench state authority in defined territorial spaces. Historically, international law developed with the territorial entrenchment of states—from Europe in the 17th century, through Latin American independence in the 19th century, and into the process of decolonization following World War II. Prohibiting annexations is critical to this project. If annexations were permitted, state authority in any given territory would be more susceptible to disruption or revision.
The second project fosters peace among independent, territorially defined states. Popular movements to limit or end interstate wars developed in the late 19th century in Europe and the Americas. Eventually, these movements helped create the League of Nations, the Pact of Paris, and the United Nations, all of which made peace a core ambition. Although the project to secure interstate peace has not been limited to preventing wars over territory—it has also sought to prevent other kinds of interstate wars—the prohibition of annexations has nevertheless been central to it.
The third project aims to realize the self-determination of the peoples within territorially defined states. Self-determination is an emancipatory project that was central to the process of decolonization. Early 19th century claims to self-determination in Europe began to challenge forcible territorial annexations that failed to consider the wishes of the people who lived in the annexed territory. After World War II, newly decolonized and non-aligned states led the push to end annexations as part of a broader agenda on self-determination. Today, the parameters of the right to self-determination are contested, but to the extent that annexations forcibly impose on peoples the authority of a foreign power, they also violate the right to self-determination.
Because each of these three projects is independently foundational to modern international law, so too is the prohibition on annexations itself. Among contemporary analysts, however, this prohibition is poorly understood and often overlooked.
The most common misconstruction conflates it with the project on interstate peace. Some argue that annexations are unlawful because they result from unlawful uses of force. Likewise, the end of the doctrine of conquest—which permitted annexations—is often described as the result of the project on interstate peace. These characterizations are oversimplified, and at times inaccurate. The prohibition of annexations and the doctrine of conquest both regulate the acquisition of sovereign title to territory, an issue that is distinct from the regulation of war and tied to all three normative projects, rather than just one.
The lack of clarity about the prohibition has significant consequences.
Regulating the use of force does not by itself resolve questions about the transfer of title to territory following the use of force. Moreover, some uses of force remain lawful. The issue has contemporary significance, for example, in the dispute around Israel’s attempted annexation of the Golan Heights, a piece of land that is part of Syria, and for various territories around the globe that are occupied.
The lack of clarity about this prohibition also systematically obscures what makes it both distinct and foundational in international law—and thus what might be the signs and stakes of its erosion. Indeed, even following Russia’s open violation of the prohibition with the 2014 and 2022 invasions of Ukraine, states rarely focused specifically on it. The international order is rapidly changing, with a geopolitical contest to “remake” the world in full swing. In this worldmaking contest, Russia’s conduct in Ukraine has been just one piece in a broader set of geopolitical developments that together threaten the prohibition of annexations and put interstate conflicts over territory back on the international agenda, with potentially devastating consequences for the world.
In their article, Brunk and Hakimi trace the origins of the prohibition of annexations in the pre-World War II period and show how it finally crystallized in international law — not with the UN Charter at the end of World War II, but in the decades after the Charter was adopted, as part of a broad push for self-determination in the process of decolonization. They analyze the prohibition’s connections to other key doctrines in international law and examine signs of its erosion.
They conclude by underscoring that, while this prohibition helps to solidify unjust territorial divisions and otherwise to support an inequitable world, it also protects vitally important values that have, for well over a century, defined the field.
“The Prohibition of Annexations and The Foundations of Modern International Law,” a Vanderbilt Law Research Paper and Columbia Public Law Research Paper, is forthcoming in the American Journal of International Law. The authors are Ingrid Brunk, Helen Strong Curry Chair in International Law and Monica Hakimi, William S. Beinecke Professor of Law at Columbia Law School.
The full paper is available at SSRN: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4806600
