This article analyses the European Union’s (EU) internal security policy as a core element of the Area of Freedom, Security and Justice (AFSJ) established by the Treaty of Amsterdam in the 1990s. In official EU internal security documents, the AFSJ has been gradually replaced by the label Security Union since the mid-2010s. Even if internal security became a fully integrated part of the new EU when the Treaty of Lisbon entered into force in 2009, the member states’ governments and intergovernmental patterns still play an important role in this policy area, as security agencies and justice institutions still differ significantly between the member states. Despite the increased importance of the EU Charter of Fundamental Rights, the member states’ strong role and the trend towards a Security Union are challenges for the establishment of rule-of-law style internal security structures in the EU.