Towards a General Part of EU Criminal Law? Autonomous Interpretation and the Attempt to Travel for Terrorist Purposes Under Directive 2017/541 as a Case Study

Article 83 TFEU allows the EU to adopt minimum rules on the definition of criminal offences. These rules often require Member States to criminalise attempt, even though the relevant directives neither define the concept nor refer it to national law. This article asks whether 'attempt' in Article 14(3) of Directive 2017/541 may consequently acquire an autonomous EU meaning when applied to travel for terrorist purposes. It argues that such an interpretation would concern the minimum conduct covered by that particular criminalisation obligation, without creating a general EU doctrine of attempt or displacing national rules outside the Directive's scope. The argument is developed through the Court of Justice's case law on autonomous concepts, the competence limits of Article 83 TFEU and the principle of legality. A comparison of Belgium, France, the Netherlands, Germany and Spain reveals materially different thresholds of liability. Some systems require the objective commencement of physical departure, while others permit liability to arise from sufficiently concrete travel preparations accompanied by terrorist intent. These differences raise uncertainty about what the EU minimum actually requires. The Directive's preventive rationale may support an earlier threshold, but effectiveness cannot justify unlimited criminalisation. Any autonomous interpretation must respect legality, foreseeability and proportionality. The case study illustrates how undefined general part concepts may become points of judicial harmonisation even where the EU legislature has not harmonised national doctrines as such.