This essay explores the fear of secession in two different context: the exit of a member State from EU and the secession of a territorially concentrated group from a member State of the EU. The case of the recent Brexit and the crisis in Catalonia are taken as case studies to comprehend theoretically which secession could «constitute» EU as a Federation. In the second part, I exemplify how from the international perspective secession can be considered as an «ultimate right» and (...) that if one can talk of such a thing as legality when referring to secession that can be done only in the sense of a liminal legality: a legality that reside in the border area between the internal and the international legal order. In the last part of the essay, I shall try to use Catalonia as test to evaluate both the opinion of the International Court of Justice on Kosovo and the famous Reference of the Canadian Supreme Court on Québec. In the conclusion of the essay, I will also verify if Catalonia can be read through the lens of the Just-Cause Theories of Secession. (shrink)