The right to self ‑determination, alongside the obligation to respect state constitutional order can be rather controversial. The right to create one's own state is established in international documents. However, is the right to self ‑determination is a mandate of international law or just a principle, especially since international law prohibits the violation of state territorial integrity? Respect for sovereignty, territorial integrity and constitutional order provide the grounds upon which a state can reject calls for secession of the people living within its territory. This is also confirmed in practice. In this regard, the intention of Catalonia to declare independence from Spain and the constitutional context of the establishment of an independent Republic of Croatia are presented.