The issue of citizenship deprivation has become an increasingly relevant topic in the struggle against terrorism. It is related to different conceptions of citizenship as well as the question of what is at stake in the process of depriving individuals of it. In the United Kingdom three acts have been passed in the 21st century so far that has reduced the requirements needed for the to deprive individuals of their citizenship and also to render individuals stateless. This thesis systematises the arguments made in the academic and political debates related to these acts and evaluates their legitimacy in relation to different normative standpoints. The main conclusion regards a logical inconsistency in the differentiation of two types of British citizenship, one where individuals have naturalised, the other where they are native born Britons, the latter may not under British law be rendered stateless while the former can be, although both have the status of citizen, which becomes problematic in terms of equality before the law and equal rights.

The revival of citizenship deprivation raises numerous normative, legal and practical concerns. Although citizenship deprivation is not new, it has become crucial to further discuss this with regards to recent law amendments and practices on citizenship deprivation by many democratic states. Sweden is still one of few countries where citizenship is an absolute right protected by constitutional law. Nonetheless, politicians in Sweden have, over the last years, discussed the possibilities to enact the constitution to legalise denationalisation based on national security grounds. Several motions have been submitted to investigate these possibilities, but no amendments have yet been proposed.  The thesis aims, therefore, to examine whether there are legal obstacles that limit the possibilities to introduce a new provision on citizenship deprivation in Sweden. The main research question is: Are there legal obstacles to tackle terrorism through denationalisation in Sweden? To answer this question, the legal dogmatic methodology is used. The study analyses legislative sources, case law and doctrinal literature. It also reviews national regulations on citizenship deprivation in five European countries that have reformed their Citizenship Acts.  The study concludes that there are several legal obstacles in both international and EU law that limit the possibilities to denationalise citizens. However, it is not entirely illegal to deprive individuals of their citizenship. To introduce the possibility of citizenship deprivation in Sweden, the provision should fulfil the following criteria: a) denationalisation should not render a person stateless, b) the provision should not be discriminatory and apply to all citizens with dual citizenship, regardless of how they became citizen, c) prior to making the decision on denationalisation, a proportionality assessment between the individual's interest and the state's interest should be applied, d) denationalisation should have a legitimate purpose and it should be the least burdensome procedure to achieve this purpose, e) Swedish law should identify the crimes that can lead to denaturalisation, f) the decision on denaturalisation should be made at the same trial as the person in question is convicted, g) the individual should have the possibility to appeal the decision and his right to a fair trial is granted.  To conclude, the thesis emphasises that the collective development in national laws and practices on citizenship deprivation will potentially lead to a new interpretation of both EU and international law on human rights.