This study provides a comparative analysis of the national legal regimes and practices governing the use of intelligence information as evidence in the United Kingdom, France, Germany, Spain, Italy, the Netherlands and Sweden. It explores notably how national security can be invoked to determine the classification of information and evidence as 'state secrets' in court proceedings and whether such laws and practices are fundamental rights and rule of law-compliant. The study finds that, in the majority of Member States under investigation, the judiciary is significantly hindered in effectively adjudicating justice and guaranteeing the rights of the defence in 'national security' cases. The research also illustrates that the very term 'national security' is nebulously defined across the Member States analysed, with no national definition meeting legal certainty and "in accordance with the law" standards and a clear risk that the executive and secret services may act arbitrarily. The study argues that national and transnational intelligence community practices and cooperation need to be subject to more independent and effective judicial accountability and be brought into line with EU 'rule of law' standards.