What happens when a new State emerges? Is it bound by the international commitments of its predecessor? There are a couple ways in which a new State can emerge, and these have potentially different implications. A State can become independent from a colonial power, entering the community of nations as a peer (as was common in the three decades following World War II). States can be created with the dissolution of a former State (for example with the Soviet Union, Yugoslavia, and Czechoslovakia). States can also be created by combining previously independent states.
When a new State emerges, the international law of succession applies. Succession provides that a new State inherits the international obligations that its predecessor had made. In the 1950s and 1960s, many African colonies achieved independence. While some followed the doctrine of succession (such as Nigeria), others followed the Nyerere Doctrine of selective succession to treaties. Julius Nyerere, the first President of Tanzania, considered that international agreements dating from colonial times should be renegotiated when a State becomes independent, as the nation should not be bound by something that the nation was not in a sovereign position to agree to at that time. According to this doctrine, a newly independent State can – upon independence – review the international treaties that it stands to inherit and decide which of the agreements it will accept and which it will repudiate. Although such an “optional” approach to events of State succession was not new and was already recognized by customary international law, Nyerere is recognized for the modern formulation of the optional doctrine of the law of State succession.
This “optional doctrine” is more refined than that of the tabula rasa, the classical doctrine of clean slate, under which a new State starts without any of the obligations of the predecessor State. Under the Nyerere Doctrine, this is only an assumption, as the doctrine does not rule out or prejudice the possibility or desirability of renewal (after a legal interruption during the succession) of commitments or agreements of mutual interest to the parties concerned. This doctrine however rejects any categorization of international obligations between those which the successor State would have to accept and those which it could reconsider. Nyerere also created a formula for the practical application of this doctrine, which provides for an interim reflection period during which some of the predecessor’s treaties apply provisionally while the successor chooses which treaties it will renew or renegotiate and which it will set aside.
Both the doctrine and the formula, with country-specific variations, served as a framework for State succession in East African States as well as for many other emerging developing countries. In most instances, predecessor States and third-party States have accepted – if not indeed supported – the application of the Nyerere Doctrine.
For more information, see (for example) State Succession and the New States of East Africa, by Yilma Makonne
"United nations environement programme" http://www.unep.org/dec/onlinemanual/Compliance/Resource/tabid/594/Default.aspx