The Right to Self-Determination of Modern Secessionist Movements under International Law

States’ boundaries have changed to a large extent over the course of time, in fact, the world has not always been the same as nowadays. In place of archaic forms of social organisation, the universal order has appeared where determinate and inviolable borders play a crucial role in ensuring the stability of states and resisting separatist movements. At the same time, secessionist movements throughout the world continually aim to gain independence from the ‘parent’ state invoking the right to self-determination. In this paper, the researcher will examine whether a part of the population of a state or a sub-unit of that state has a right to secede and create a new state and/or integrate into another. The article consists of a strong theoretical part dealing with statehood, self-determination and secession with a view of the dynamic development of these notions since the rapid birth of many new states as a result of decolonization. Thereafter, the validity of the gathered results will be verified by a comparative analysis of the cases of Kosovo, Crimea and Catalonia with regard to the historical background of these secessionist entities.