The paper analyses the struggles of the Catalan Government to organise a referendum on secession and the Constitutional framework invoked by the Spanish central authorities to prohibit it. On then one hand, it shows that the repression of secessionist referendums within the Spanish Constitutional framework triggers several problematic questions concerning the role of constitutional supremacy in handling with subnational secessionist challenges developed under a pacific and democratic framework. On the other hand, the paper describes the political, historical and legal circumstances surrounding the Spanish central authorities‘ actions in order to explain Spain’s constitutional response to the Catalan challenge. The paper argues that the prohibition of the Catalan independence referendum initiatives cripple the basic pillars of the Spanish liberal democracy designed under the 1978 Spanish Constitution.