In recent years, numerous European states have resorted to citizenship deprivation to tackle the security threat posed by foreign fighters. This Chapter analyses the rule of law and human rights impact of the deprivation of citizenship of foreign fighters in the United Kingdom and the Netherlands. In the context of the United Kingdom, the Chapter examines the consistency of the UK’s legal regime with international legal obligations on the reduction of statelessness as well as the role of judicial deference to the executive, zooming in on recent jurisprudential developments that were brought to the fore by the landmark case of Shamima Begum. In addition, the Chapter unpacks the set of administrative measures specifically aimed at foreign fighters that were introduced by the Counter-Terrorism and Security Act 2015, in particular ‘Temporary Exclusion Orders’. Furthermore, the Chapter assesses whether the practice of depriving foreign fighters of their citizenship violates the ECHR and the European Convention on Nationality, examining the ramifications of the citizenship deprivation of foreign fighters on the international legal orderInternational legal order and international relations. Beside interfering with human rights, citizenship deprivation of foreign fighters contravenes international obligations to bring terrorists to justice, first and foremost those deriving from the international legal regime on foreign fighters, including UN Security Council Resolution 2178. The Chapter concludes that the metamorphosis of citizenship deprivation from an obscure tool of totalitarian regimes to one of the flagship counter-terrorism policies of liberal democracies is disconcerting from the perspective of the rule of law and human rights.