Action by both Crimean and Russian public authorities for the purpose of making the Crimean Peninsula part of the territory of the Russian Federation has given rise to a hot political debate and to a prolific flow of legal doctrinal literature. Most Western authors agree with the prevailing view among Western politicians that this was an annexation which was unlawful and therefore invalid. But most legal assessments of the situation stop at this point. They do not address the question as to the ensuing status of the Crimea under international law and what are, as a consequence, the rights and duties of its inhabitants as well as the rights and duties of third States. The present paper aims at examining several legal aspects of the situation, with a focus on the following issues : what is the legal status of the territory assuming that the annexation by the RF is indeed unlawful ? What are the rights and duties of the population in case of a valid or of an invalid alteration of the territorial status ? What are the rights and duties of third States in relation to an invalid annexation ? What are practical options to deal with the problem ?