How does the Vienna Convention on the Law of Treaties go about such cases when one of the two sides stops existing? For example, when USSR stopped existing how did the Vienna Convention regulate all the treaties and agreements that had been signed between the USSR and other countries?

I've looked through the text of Convention, but couldn't quite find anything related to such cases. Is it like the Convention only considers cases when all sides of treaties and agreements still exist?

3 Answers 3


There are two main cases to distinguish.

1) There is a successor state. This is an easy case. The successor state takes on all treaty obligations unless specifically decided otherwise. Russia is the successor state of the USSR.

2) There is no successor state, either because the original state is conquered or too fragmented. South Vietnam would be an example of conquest, Yugoslavia of fragmentation. This is also fairly easy - there is no successor state, so the treaty stops applying to the defunct state. For a bilateral treaty, that means the end of the treaty, a multilateral treaty in general survives.

However, international politics is generally more descriptive than prescriptive. There are always edge cases. E.g. the dissolution of Czecho-Slovakia did not lead to a designated successor state. However, as part of the planned and peaceful divorce, both the Czech Republic and Slovakia accepted obligations from prior treaties, and were (as far as I can tell) both accepted as new signatories to existing treaties.

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    It would probably be good to reference and link to the Vienna Convention on Succession of States in respect of Treaties Nov 6, 2018 at 16:57
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    @Burt_Harris: That's a rather obscure Treaty with few signatories.
    – MSalters
    Nov 8, 2018 at 7:49
  • that's an interesting observation. It does seem relevant to the question, as its intended to supplement the earlier VCLT, and was acceded to by some former soviet republics, for example Ukraine. Nov 10, 2018 at 12:27
  • Are you sure all treaties stopped to apply to the ex-Yugoslav Republics? Serbia-Montenegro certainly maintained a claim to be a successor state for a long time and would have had an interest in fulfilling Yugoslavia's obligations (whenever other states or organisations would let them). Ultimately, there was on agreement in which Serbia-Montenegro (the “Federal Republic of Yugoslavia“), Croatia, Slovenia, (Northern) Macedonia/FYROM, and Bosnia-Herzegovina claimed to be equal successor states, undermining the notion that there is no successor state.
    – Relaxed
    Apr 18, 2019 at 20:54
  • One caveat applies to 2). The treaty survives even if the state doesn't survive, if it is "obvious" that the treaty should survive. This mostly applies to border arrangements which are not nullified by either party ceasing to exist but can also apply to treaties about water resources and such. Apr 19, 2019 at 1:46

This history answer provides a more general answer that is not only related to treaties, but also to other issues that have risen when the Soviet Union collapsed:

(..) Russia inherited the debt, the properties abroad (embassies &c), operational control over Nukes, treaties, including UNSC permanent membership, nuclear status in the NPT

The same answer provides reasons about why virtually all countries were fine with replacing USSR with Russian Federation in the treaties:

They were so overjoyed with the end of the Cold War that they bent over backwards to welcome Russia "back into the fold". They were also concerned with non-proliferation, so they wanted all nukes under a single control.

Of course, Russia's case is somewhat special as USSR collapse resulted in a country that has something to say in global politics and for smaller countries there might be need to reapply to some treaties.


The situation with Russia vis-a-vis its status as a continuator state of the USSR could not be resolved based on the established conventions alone.

To be clear, all 15 of the former Soviet Republics were successor states of the USSR by the definition of what a successor state is. A successor state is simply a state which inherits a former state's territory (so East and West Germany were successors of Germany and the modern-day Germany is a successor state of both East and West Germany). This is just how the modern-day UN defines the term "successor state."

Succession of states is a concept in international relations regarding a successor state that has become a sovereign state over a territory (and populace) that was previously under the sovereignty of another state. The theory has its roots in 19th-century diplomacy.

A "continuator" state is a state which results from a former state transforming itself into a newer form. So, for example, the USSR was a continuator state of the Russian Empire. I think there is probably an argument that can be made either way about whether Poland and Finland were successor states of the Russian Empire, or whether they were break-away former colonies of the Russian Empire.

As someone mentioned, in a comment I read somewhere else on this site, Bulgaria would be a counter-example of a continuator state because the modern Bulgaria established itself as de jure same state as the Communist Bulgaria, but only with a very different legal system.

Because there was so much interdependence between public works projects of different regions of the USSR, simple succession could not solve the rights of succession. In order to avoid conflicting claims, a series of bilateral agreements were established, which gave some of the new states limited rights over the properties owned by other states.

For example, the Russian Federation still rents its orbital-launch facilities from Kazakhstan. And until 2008, the Russian Federation had a treaty allowing it rent the port facilities in Crimea from Ukraine (the legal owner of Crimea). The legality of the renting agreement was probably violated when the Russian Federation refused to abide by the rental agreement during its war against Georgia (in 2008).

The main confusion comes form the Russian Federation claiming the USSR's UN Security Council seat. There are other questions, on this site, about that issue. Suffice it to say, that initially it was a thorny issue because all 15 former Soviet Republics were new states and all 15 were successor states.

So there was a theory under which all 15 could press for a right to a UNSC seat. Since this would have destabilized the UN, the status quo of Russia retaining USSR's seat remains because no formal procedural challenge to it has been presented.

By UN conventions, when the established norms are not clear with regards to any specific question of succession, the succession is guided by bilateral agreements. So, for example, the USSR never signed a peace treaty with Japan because a peace treaty would have to settle all territorial disputes of the conflict. And the dispute over some islands was never settled. After the voluntary dissolution of the USSR by the December 26th, 1991 resolution of the Supreme Soviet of the USSR, all 15 new states were free to make their own treaties with Japan.

  • Not sure I get the Bulgaria point.
    – alamar
    Sep 5, 2023 at 8:23
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    @alamar it's a counter example because despite the government looking like it's a new country which is a continuator of the old country, it's not. It's the same country which changed its laws to have a different legal system. Changing laws doesn't make an old country into a new country. Countries change their laws all the time. It, in itself, doesn't change (for example) their relationships with respect to other countries.
    – wrod
    Sep 5, 2023 at 23:29

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