The presentation begins with introductory remarks centred principally on the topicality of the legal status of dual nationals. Whereas earlier the doctrine of State sovereignty required that an individual have only one nationality, the status of dual nationality is now increasingly accepted, though not created, by States. The development of human rights law is of importance insofar as statelessness is now considered to be a greater evil. It then continues with some basic principles in international law, the first being that it is for each State to decide who are its nationals. This leads to a discussion of some landmarks in the development of the international law of nationality: the Tunis and Morocco Nationality Decrees before the PCIJ in 1923; the League of Nations codifying Convention on Certain Questions Relating to the Conflict of nationality Laws, 1930; and the Nottebohm case before the ICJ, 1953, in particular. Te greatest contribution to the topic has come from the Iran-United States Claims Tribunal, for three reasons: for rejecting Article 4 of the 1930 Convention, embodying the principle of non-responsibility; further, it clarified how dominant and effective nationality can be determined for the purposes of the nationality of claims; and it developed the equitable doctrine contained in the caveat to Case A/18 that the status of dual nationality must not be used unjustly or fraudulently. Lastly, the possibility of a “dormant” nationality is accepted, and the European Convention on Nationality, 1997, and the International Law Commission's drafts on Diplomatic Protection noted.