What is Annexation? The Legal Process

By: Tessa Fardel

Annexation is the forcible acquisition of territory by one State at the expense of another State. (Hoffman, 2013).

Under previous international law, annexation could be effected by unilateral declaration, provided that the adversary is defeated and the territory conquered. This declaration is necessary to make the annexation effective since it announces the intention of the State to acquire not only jurisdiction over the territory in question but also territorial sovereignty.

The second way to annex the territory of another State is by the conclusion of a treaty. In this case, the transfer of territory is also done under compulsion, since the ceding State is either being forced to sign the peace treaty after a military defeat, agreeing to a transfer of territory as a consequence of a threat of the use of force, or the State is represented by a “puppet government” prepared to accept the annexation (Hoffman, 2013).

The discussion on the legality of annexations started in 1919 with the League of Nations Covenant, which guaranteed the territorial integrity and political independence of States and restricted the right to wage war.

Then, the Kellogg-Briand Pact of 1928 prohibited war as a means to achieve political aims. As a result, wars of aggression being increasingly considered to be unlawful, the acquisition of territory following them were also considered to be invalid.

Under present international law, those modes of acquisition of territory are no longer legal. What are the legal bases of the prohibition of annexation? What practical challenges this prohibition implies?

The Prohibition of Annexation Under International Law

Since the beginnings of the UN Charter, and especially through its articles 2§3 and 2§4 that provide for the obligation of peaceful settlement of international disputes and for the prohibition of the use of force, annexations are illegal.

Nevertheless, international law is often characterized by the lack of a centralized form of executive power. If the Security Council bounding decisions can help to enforce the UN Charter’s provisions, this enforcement is not carried out by a centralized police force as it exists in domestic law (Bering, 2017).

Since the Vienna Convention on the law of treaties of 1969, through its article 52, any treaty is void if its conclusion has been procured by the threat or use of force. Therefore, any treaty-based annexation couldn’t be considered as valid under present international law.

This prohibition also stems from customary international law.

Indeed, in international law, the principle Ex injuria jus non oritur provides that no right can arise from an unlawful fact. As a result, third party States shouldn’t recognize annexed territories as a part of the aggressor State (Bering, 2017). If some authors consider the principle as being a rule of jus cogens, i.e. a peremptory rule, it has often been criticized and considered as being unrealistic.

Nevertheless, if its practical utility can be discussed, this principle has been recognized several times as a customary rule by the International Court of Justice and the International Law Commission.

This position seems to have been confirmed by a consistent State practice. Although State practice is difficult to observe when the rule prohibits an activity, we can note that annexation cases are rare (Bering, 2017).

With the Stimson doctrine, that emerges after the Japan’s unilateral seizure of Manchuria in north-eastern China following Japanese military conquest in 1932, the United States follow the provisions of the Kellog-Briand Pact and the principle of ex injuria jus non oritur, by refusing to recognize international territorial changes that were executed by force.

If the recognition of a State isn’t sufficient to establish its legal existence, its practical implications are significant. Indeed, the recognition will allow the State in question to conclude treaties, to join international organizations, and will grant legal effects to its legal acts (Corten, Dubuisson, Koutroulis, & Lagerwall, 2017).

What is important here, is that the prohibition of annexation can’t be implemented without its corollary: the obligation of non-recognition of annexed territories for third-party States.

If this position emerges before the entry in force of the UN Charter with the Stimson doctrine, it’s through several resolutions from the UN Security Council (binding decisions) and from the UN General assembly (non-binding decisions that express the Member States’ interpretation of International Law) creating an evidence of opinio juris, that this viewpoint has been endorsed.

To that extent, we can mention the General Assembly Resolution 3314 (XXIX) that states that “no territorial acquisition or special advantage resulting from aggression is or shall be recognized as lawful”.

In the context of Iraq-Kuwait War, the Security Council declared Iraq’s annexation of Kuwait to be null and void, and that no Member States shall recognize it. We can also mention that the Security Council reaffirms “the commitment of all Member States to the sovereignty and territorial integrity” of other states in several resolutions.

Those examples illustrate the “strong commitment of the international community to outlaw annexation” (Hoffman, 2013). Such a strong commitment combined with a rather uniform State practice confirms that under present international law the prohibition of annexation and the obligation of non-recognition of third-party states constitute a customary rule.

Challenges to the Prohibition of Annexation

In the case of an annexation through a peace treaty, if we explained the invalidity of the process because of the compulsion element of the conclusion, two situations need to be developed.

First, the legality of the treaties concluded before the emergence of the prohibition of the use of force in international relations and the Stimson doctrine can’t be questioned since the present international law shall not be applicable.

Second, if a peace treaty is concluded and it is proven that the ceding State freely accepted the cession of territory, the legality of the treaty couldn’t be questioned either, since the illegality arises from the element of compulsion, itself being a violation of the prohibition of threat or use of force.

Although the obligation of non-recognition is well accepted as customary law, what would be the effects of an explicit or tacit acceptance of such acts by the international community on the validity of the annexing State’s title?

The recognition of annexed States by third-party States isn’t itself sufficient to establish the legality of the situation. Nevertheless, we could consider the application of the principle of effectiveness, according to which the passage of time and the undisturbed possession would lead to a historical consolidation.

According to Rainer Hoffman, the more convincing view would consist in rejecting the applicability of the legal institute of historic consolidation with respect of the acquisition of territory by annexation since the ban on annexation arise from the prohibition of the threat or use of force being a fundamental pillar of present international law (Hoffman, 2013).

An important challenge resulting from the prohibition of annexation is the legal situation of the population of the annexed territory. Indeed, how should the third-party State interact with individuals, when any legal acts of sovereign authority by the annexing State shall be legally null and void?

The annexation being per se the result of military occupation, the rules of belligerent occupation should be applied to the inhabitants of the annexed territories.

Because of the numerous legal and practical problems that this situation can imply for the population of annexed territories, a State practice has emerged which apply the principle of effectiveness, in the sense that it would allow for some pragmatism regarding the legal status of those populations.

This de facto recognition of annexation through some acknowledgment of the legal acts taken within the annexed territory is practiced by many States without prejudice to their official position of non-recognition of the annexation situation.

The Annexation of Crimea

On March 1st, 2014, a few days after the collapse of the pro-Russian Ukrainian president Viktor Yanukovych, Russia authorized the deployment of military troops in Ukraine (Iakimenko & Pachkov, 2014).

On March 16, a referendum was organized by the Crimean regional government, asking the Crimean people to decide either to become a part of the Russian Federation or to restore the 1992 Crimean constitution allowing the region to stay in Ukraine with a more autonomous status.

With 96.77% vote for the integration of the region into the Russian Federation, Vladimir Putin declared that Crimea is officially part of Russia on March 18 (Dolya, 2016).

On March 27, the General Assembly of the United Nations adopt a resolution (non-binding) supported by 100 Member States, expressing its commitment to Ukraine’s territorial integrity and the invalidity of the referendum. Several economic, political and military sanctions have been taken by international actors like the United States or the European Union. (Messina, 2014).

The annexation of Crimea by Russia shows the lawfulness of the prohibition of annexation and the effectiveness of public international law. Indeed, the Russian position isn’t to deny the validity of this prohibition but to actually prove that its actions are in conformity with public international law.

This way, Russian authorities have argued that their actions were truly supporting the right of self-determination of the Crimean people and emphasized that it was not a case of annexation.

This position shows that annexation is considered as being out-limit, and no actor has argued that annexation wasn’t illegal, neither in general nor in this specific case. Russia agrees with this prohibition being part of public international law, even though it violates it.

This case shows how a breach of international law can actually support the existence of a rule, and especially of a prohibition. Russian actions entailed a strong international reaction, that can be seen as further evidence of the belief of the validity of the rule.

We can summarize the third-party State’s reaction to the event with Eric Posner's words: “1. Russia’s military intervention in Ukraine violates international law. 2. No one is going to do anything about it”.

If no military actions have been taken, unlike for the Kuwait annexation by Iraq for example, the reactions condemning the annexation of Crimea are significant concerning the strength of the customary rule.

It may also be argued that such a strong reaction punishing the violation of this rule may even reinforce it and help to prevent future violations (Bering, 2017).

If it is clear that annexation is prohibited by public international law, as constituting a violation of the fundamental rule of international relations that is the prohibition of threat or use of force, we have seen that it’s implementation isn’t absolute.

The humanitarian necessity of protecting the population of the annexed territories has lead the third-party State to have a de facto practice that nuances the practical implementation of the obligation of non-recognition.

Furthermore, international sanctions and critics carry a political weight that might prevent stronger responses, as we could have expected in the case of the annexation of Crimea.

Nevertheless, the strength of this customary rule is significant. As its violation by Russia show, it is well accepted among the international community that annexation can’t be in any case legal. The prohibition of annexation and the obligation of non-recognition might even be considered as being jus cogens rules, i.e. peremptory rules.


Bering, J. (2017). The prohibition of annexation: Lessons from Crimea. University Journal of International Law and politics, pp. 747-832.

Corten, O., Dubuisson, F., Koutroulis, V., & Lagerwall, A. (2017). Une introduction critique au droit international. Bruxelles: Editions de l'Université de Bruxelles.

Dolya, A. (2016). L'annexion de la Crimée : leçons pour la sécurité européenne. Fondation Robert Schuman.

Hoffman, R. (2013, Février). Annexation. Max Planck Encyclopedias of International Law.

Iakimenko, I., & Pachkov, M. (2014). Le conflit ukraino-russe vu de Kiev. Politique étrangère, pp. 81-93.

Messina, M. (2014). Le détail des sanctions internaitonales contre la Russie. Le Monde.

#Annexation #Crimea #UnrecognizedCountries #AnnexedRegions

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