Abstract
Although under EU Law Member States are free to define their internal or national security, the interpretation of these terms and their application are subject to interpretation by the CJEU. This happens when the security argument is being used by a Member State for the purpose of derogation from EU law.
It is a task of the CJEU to evaluate the legitimacy of the security argument. CJEU case-law therefore presents constraints on Member States regarding how the notion of internal security should be interpreted.