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?


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 – Burt_Harris Nov 6 '18 at 16:57
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    @Burt_Harris: That's a rather obscure Treaty with few signatories. – MSalters Nov 8 '18 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. – Burt_Harris Nov 10 '18 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 '19 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. – Björn Lindqvist Apr 19 '19 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.

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