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State succession refers to the process in which two or more States merge or undergo a change. It should be distinguished from government succession, where there is a change in the ruling government. State succession involves a State losing control over some or all of its territory. According to Article 2(1)(b) of the 1978 Vienna Convention on the Succession of States in respect of Treaties, State succession is defined as "the replacement of one State by another in the responsibility for the international relations of territory."
In essence, State succession deals with the transition from one State to another and the transfer of associated rights and obligations. This concept has gained significant importance since World War II due to its impact on the legal responsibilities of States.

Circumstances of State Succession 

State succession can occur under specific circumstances, which reflect how political sovereignty is acquired.
These circumstances include:

  • Decolonization of an entire or part of an existing territorial unit: This situation involves a nation freeing itself partially or completely from the control of a more powerful nation.
  • Dismemberment of an existing State: This scenario occurs when the territory of the original State becomes the territory of two or more new States, each assuming control over a portion of it.
  • Secession: This refers to a situation where a region within a State decides to separate from the existing State and establish itself as an independent entity.
  • Annexation: Annexation takes place when one State takes control and ownership of another State's territory.
  • Merger: This involves the consolidation of two or more independent States into a single, unified State.

Types of State Succession 

In all of these scenarios, an entity that was once recognized as a State either completely or partially ceases to exist, giving way to a new governing authority. This transition raises issues concerning the transfer of rights and obligations, and there are two main types of State succession:

Universal Succession (Total Succession)

Universal succession, also known as total succession, occurs when the entire identity of the original State is extinguished, and the former territory assumes the identity of the successor State.
This can happen in cases involving:

  • Merger: When two or more States merge to form a single new State.
  • Annexation: When one State takes control and ownership of another State's territory.
  • Subjugation: When a State is forcibly brought under the authority of another State.

In some instances of universal succession, the original State may split into multiple new States. An example of this is the dissolution of Czechoslovakia, resulting in the successor States of the Czech Republic and Slovakia.

Partial Succession

Partial succession occurs when a portion of a State's territory becomes separate from the parent State and gains independence, forming a new State. This can happen during situations such as civil wars or struggles for self-determination.
Two significant examples of partial succession are the separation of Pakistan from India and the later separation of Bangladesh from Pakistan. In such cases, the existing parent States continue to carry out their legal obligations and responsibilities, while the newly formed States gain recognition as independent entities, assuming their own rights and responsibilities.

Theories of State Succession 

Universal Succession Theory 

The Universal Succession Theory, originally proposed by Grotius, draws an analogy from Roman law, likening the succession of States to the passing of rights and duties that occurs upon the death of an individual. According to this theory, when a new State succeeds an old State, all the rights and obligations of the former State automatically transfer to the latter without exceptions or modifications.
There are two main justifications behind this theory:

  • The idea that both the State and the Sovereign derive their authority from God, and a mere change in government should not result in any alteration of their powers.
  • The notion that this succession is permanent and cannot be undone.

This theory has been applied in cases of state fusion during the 20th century, such as the merger of Syria and Egypt, Somali Land and Somalia, and Tanganyika and Zanzibar. However, it has not gained widespread acceptance among the majority of States globally and has faced criticism from scholars due to its reliance on Roman law analogy, a lack of clear distinction between succession and internal government changes, and other factors.

Popular Continuity Theory 

The Popular Continuity Theory can be seen as a variant of the Universal Succession theory and was developed by Fiore and Fradier following the unification of German and Italian nationals.
According to this theory, a State has two distinct personalities:

  • Political personality: This refers to the rights and obligations of the State concerning its government.
  • Social personality: This pertains to the territory and population of the State.

Under this theory, when succession occurs, the political personality changes, but the social personality remains unaffected. Consequently, State succession should not alter the rights and responsibilities of the population.
However, this theory has not been applied outside of Europe and has faced criticism for relying heavily on municipal laws, making it difficult to comprehend the effects of State succession.

Organic Substitution Theory 

The Organic Substitution Theory posits that the rights and responsibilities of a State persist even after it has been succeeded by another State. This theory originated from Max Huber, who drew parallels between the issue of State succession and the dissolution of a social institution. Huber argued that the connection between the people and the territory of a State is organic, and even when a new sovereign takes over, this organic connection remains intact, with only the legal aspect changing. This theory offers a fresh perspective on the continuity of rights and obligations, suggesting that the successor State essentially replaces its predecessor in the role of the State. However, like other theories, it has not been practically applied and has faced criticism.

Self-Abnegation Theory 

The Self-Abnegation Theory, proposed by Jellinek in 1900, is another variant of the universal theory of continuity. According to this theory, the successor State agrees to adhere to international law rules and fulfill obligations created by the predecessor State. While it acknowledges that the performance of international obligations is a "moral duty" of the successor State, it also grants other States the right to insist that the successor State honor the predecessor's commitments. If the successor State refuses, other States may withhold recognition or condition recognition on the acceptance of the predecessor's obligations.

Negative Theory 

The Negative Theory, developed in the mid-19th and early 20th centuries and emphasized by Soviet jurists after World War II, focuses on the right to self-determination and the freedom of States to maintain their international relations. According to this theory, the successor State does not inherit the political and economic interests of the predecessor State. Instead, upon succession, the new State is free from the obligations of the predecessor State. The successor State does not gain jurisdiction over the territory through a transfer of power from the predecessor; instead, it acquires the potential to expand its own sovereignty.

Communist Theory 

The Communist Theory of State Succession contradicts the Negative Theory by asserting that a successor State is bound by the economic and political commitments of its predecessor. Unlike the Negative Theory, it does not release the successor State from the obligations of the predecessor State. According to this theory, the successor State must fulfill the commitments of the predecessor State, including political commitments such as peace, war, and territorial treaties, as well as economic commitments, such as borrowed or lent funds.

Rights and Duties Arising from State Succession

The laws concerning State succession are continuously evolving and remain relatively undeveloped. State succession involves not only the transfer of territory and power but also the transfer or non-transfer of various rights and duties. This section provides a brief overview of the transfer and non-transfer of political and non-political rights and duties.

Political Rights and Duties 

  • State succession does not result in the automatic transfer of political rights and duties from the predecessor State to the successor State. 
  • Peace treaties or neutrality treaties that were previously entered into by the predecessor State do not bind the successor State. 
  • However, an exception exists for human rights treaties, as it is desirable for the successor State to adhere to such agreements. 
  • The successor State is typically required to negotiate and enter into new political treaties independently.

Local Rights of Natives 

  • Local rights of the people, such as property rights, land rights, and rights related to infrastructure like railways, roads, and water, are not automatically transferred with State succession. 
  • In such cases, the succeeding States inherit the duties, obligations, and rights of the extinct State.

Fiscal Debts (State or Public Debts) 

  • Fiscal debts refer to the financial obligations or debts incurred by the predecessor State. 
  • The successor State is obligated to repay the debts of the predecessor State, as it often enjoys the benefits of the loans obtained. 
  • In the event of a State split, the total debt amount is divided between the predecessor and successor State based on their respective territories and populations.

Impact of State Succession on Treaties

The area of State succession concerning treaties has long been influenced by two predominant principles:

  • The principle of universal succession, which considers the interests of third States in upholding or not upholding treaties.
  • The tabula rasa approach, also known as the clean State doctrine, which does not grant State succession to treaties and strictly upholds the sovereignty of the successor and predecessor States.

However, neither of these principles offers practical solutions for various scenarios where State succession occurs. Consequently, customary international law has developed more nuanced solutions or is in the process of doing so.

The Vienna Convention on State Succession provides the following guidelines:

  • Border treaties and local treaties related to land and territory generally pass on to the successor State upon succession, considering the greater interests of the international community.
  • Treaties relating to human rights are transferred to the successor State along with all their rights, duties, and obligations.
  • In the case of treaties related to peace or neutrality, no succession occurs.

Impact of State Succession on UN Membership

When Pakistan was separated from India, it claimed itself to be a member of the United States since India was a member of the UN. The then Secretary-General of the UN had then brought up the following:

  • From the perspective of International Law, the circumstance is one in which part of the State breaks off from the original State.
  • When Pakistan separated from India, there was no change in the status of India. India continued with all its treaties, rights and obligations.
  • On the other hand, Pakistan didn’t have any of those rights or obligations and of course, had lost the UN Membership. 
  • In International Law, the situation is similar to the separation of the Irish Free State from Britain, and Belgium from the Netherlands. In these cases, the portion which separated was considered a new State, and the remaining portion continued as an existing State with all the rights and duties which it had before.

Thus, in the case of succession, the UN Membership doesn’t get transferred.


The field of State succession in international law requires further development and clarity. While there has been some consensus on certain aspects, it is evident that more work is needed to address the complexities and nuances of State succession, especially concerning treaties and UN membership.

The document State Succession under International Law | Law Optional Notes for UPSC is a part of the UPSC Course Law Optional Notes for UPSC.
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