Abstract Exercise of right to self-determination that ended in State succession had always come with responsibilities or obligations for the successor State. This study, among other objectives, sought to identify the legal basis of self-determination, the legal implications of State succession, and to ascertain the best approach to the Biafra agitation and how her obligations in the event of succession could be determined. It was qualitative research, dependent purely on secondary sources comprising already existing hard and soft documents. The data, being secondary, were content analyzed. Applying the Nationalism Theory, it was found, inter alia, that: self-determination was founded on international law; there were theories that determined States’ obligations on succession; State succession implied substitution of sovereignty; the best approaches to Biafra’s agitation was negotiation and/or referendum; and that the best theory was the Optional (Nyerere) doctrine of State succession. Our recommendations included good-governance and democracy; adequate enlightenment; peaceful resolution through applicable means under Art. 33(1), UN Charter; amendment to the UN Charter to declare clearly the legal status of right to self-determination; and that the Optional doctrine should be adopted wherein both Nigeria and Biafra should be involved, mutually and reciprocally, in reaching agreements.