This thesis analyses the policies aimed at influencing the situation of the Hungarian minorities in Romania and Slovakia undertaken by three European organisations, the Council of Europe, the EU and the OSCE High Commissioner on National Minorities. The focus is on the way in which the organisations have conceptualised contested concepts concerning national minorities, minority rights and minority policy in general, when reacting to the policies of the Hungarian, Romanian and Slovak states that have been directed at the Hungarian minorities. Starting with the assumption that many of the concepts upon which minority policies are based are essentially contested, the thesis sets up a framework for analysing the use of specific interpretations of such concepts in argumentation. More specifically, the framework makes it possible to look at how specific interpretations or conceptualisations of such concepts have been used as implicit warrants. By analysing the use of warrants in the texts issued by the organisations in the arguments reacting to the Hungarian minority policies of the three organisations, the thesis provides a picture of how the conceptualisations of different contested concepts developed. Furthermore, by comparing the use of conceptualisations by the organisations, it is argued that although the organisations started out from different positions, they have gradually converged. And this convergence was centred on the emergence of an ideal minority policy which framed the minorities as unitary entities, which should have the right to influence decisions affecting them as minorities. This convergence was due to the appearance of the Framework Convention on the Protection of National Minorities, increased cooperation between the organisations and the reliance of the EU on the assessments of the other two organisations in the context of EU enlargement. Yet, the organisations have often been incoherent, and have treated different issues from very different perspectives.