The choice between self-determination and territorial integrity is one of the oldest false dilemmas of International Law. It sets the problem of secession under two contradictory and mutually exclusive options, neither of which is true as such under positive International Law: either a specific group within a State constitutes a "people" and has a right to "external" self-determination; or the territorial integrity of the parent State must be respected and prohibits secession by such a group. This dilemma is very convenient from a political point of view. It provides States with the opportunity to "ride two horses at the same time". States could thus embrace 'self-determination' of some groups and encourage in one way or another separatist claims compatible with their interests, while proclaiming that the principle of territorial integrity prevails at home or in the territory of friends and allies. The case of Crimea highlighted these contradictions once again. Russia, which for years was a big champion of the principle of respect of territorial integrity of States (especially during the 90s when it was fighting the separatist attempts in Chechnya and Tatarstan), suddenly started claiming that the principle of self-determination of Russian speaking populations in Crimea prevails over the territorial integrity of Ukraine. Western States, which constantly backed in one way or another the Kosovo separatist movement since 1998 and which recognized Kosovo just a few hours after the declaration of independence on February 17, 2008, suddenly rediscovered, because of the crisis in Ukraine, the merits of the principle of territorial integrity and other basic principles of International Law often violated by these same Western States during these last years. In this article we focus on the relevance of the principle of self-determination in the Crimean conflict. We try to explain why the "dilemma" between self-determination and territorial integrity is a false one. We explain that there is no "right" to external self-determination and unilateral secession for any "people" or ethnic group outside the colonial context. But while secession is not authorized by international law neither is it in principle prohibited by the principle of territorial integrity, save in the event of violation of a fundamental rule of international law, which raises the crucial issue of the unlawfulness of Russian military intervention in Crimea and the possible solutions to the fierce conflict between unlawful effectivités and the law.