This work deals with the question of unlawful territorial situations, i.e. territorial regimes that are established and maintained in defiance of international law. It represents a very timely contribution to the debate concerning the nature, the aims and purpose of foreign interventions in the affairs of sovereign countries. International lawyers have focussed on the important questions of the legal regime applicable to the conduct of the occupant and the authoritative decision-making processes by international institutions, but often neglected the broader and decisive question of the legality of the 'foreign' or 'international' presence as such. The author shows the relevance and, sometimes irrelevance, of international law to the determination of legality or illegality of the occupation, and how legal norms incorporate and interact with the concepts of effectiveness and legitimacy.The book represents a welcome contribution to an issue of the outmost importance in international affairs at present times. It brings together elaborate theoretical discussion and thorough empirical research. Students of international law, practitioners, and anyone interested in deepening the understanding of the role and relevance of international law to territorial occupation will greatly benefit from this study.