Double Jeopardy in Cross-Border Criminal Law: The principle of ne bis in idem—the prohibition of double jeopardy—is a cornerstone of the rule of law. Within the European Union, it is enshrined in Article 54 of the Schengen Implementation Agreement (SIA) and Article 50 of the Charter of Fundamental Rights. But what constitutes the “same offense” in a borderless area where crimes often have cross-border dimensions? The Court of Justice of the European Union (CJEU) addressed this question in its judgment of September 11, 2025 (Case C-802/23).
The case involved a former leader of the terrorist organization ETA, who had been convicted in France for participation in a terrorist organization and was subsequently prosecuted in Spain for specific terrorist attacks. The CJEU’s decision clarifies the conditions under which identity of offenses, in the sense of EU law, can be established—a question of significance not only for terrorism cases but for EU criminal law as a whole.
Terrorism, Cross-Border Responsibility, and Divergent Convictions
The defendant, MSIG, had acted as a leader of ETA from France, overseeing the planning and support of terrorist attacks in Spain. French courts convicted her of “participation in a criminal association for the purpose of preparing terrorist acts” and sentenced her to a total of 20 years in prison. Spanish authorities, however, pursued her for concrete terrorist attacks, including a 1997 bombing of a police station in Oviedo carried out by an ETA commando. MSIG had issued instructions and supplied weapons from France without being physically present in Spain.
The Spanish Audiencia Nacional (National Court) faced the question of whether the prosecution in Spain violated the ne bis in idem principle, given that the French judgments already covered her role as an organizer. While the Spanish Supreme Court had ruled that no double jeopardy existed, the Audiencia Nacional referred the question to the CJEU: Did the offenses constitute the “same act”?
Interpreting the Concept of “Same Offense”
The EU Legal Framework: Article 54 SIA and Article 50 of the Charter
The CJEU emphasized that the ne bis in idem principle requires two conditions: first, a final judgment in one Member State (bis), and second, that the same factual conduct is at issue (idem). Crucially, the determination of “same offense” is not based on legal classification but on the actual conduct. The Court reiterated that this concept must be interpreted autonomously under EU law, independent of national criminal provisions.
According to consistent case law from the CJEU and the European Court of Human Rights (ECtHR), identity of offenses exists when there is an inseparable complex of circumstances involving the same person acting within the same temporal and spatial context. The legal qualification—whether as membership in a terrorist organization or as concrete terrorist acts—is irrelevant.
Application to the Case: Preparatory Acts vs. Concrete Attacks
In this case, MSIG had organized attacks from France without direct involvement in Spain. French courts convicted her for her role in the terrorist organization, while Spanish authorities sought to hold her accountable for the specific attacks.
The CJEU clarified that the key question is not whether the legal provisions are identical but whether the conduct in question is the same. If the Spanish charges essentially rely on the same actions—namely, organizing and facilitating the attacks—that were already adjudicated in France, then the offenses are identical. The Spanish court must therefore assess whether the acts prosecuted in Spain are truly new and distinct or whether they were already addressed in the French judgments.
The Court further noted that the assessment must go beyond the operative part of the judgments and consider the underlying factual findings. Under Article 57 SIA, authorities may request clarifications from the first Member State if there is uncertainty about the precise scope of a prior conviction. This highlights the importance of cross-border judicial cooperation in determining identity of offenses.
The Distinction: Preparatory Acts vs. Independent Offenses
The CJEU stressed that ne bis in idem does not apply if the offenses are merely similar rather than identical. In this case, however, the Spanish allegations appeared to be based on the same organizational acts—issuing instructions and supplying weapons—that had already been adjudicated in France.
Ultimately, the final determination of identity rests with the national court. The CJEU’s role is to ensure that differences in legal classification do not preclude the application of the principle. If the Spanish charges fundamentally concern the same conduct that MSIG carried out from France, further prosecution would be impermissible.
The ruling is a significant step toward harmonizing criminal law in the EU. It demonstrates that fundamental rights protection does not end at national borders but requires a uniform interpretation. At the same time, the case illustrates the complexity of distinguishing between legitimate prosecution and prohibited double jeopardy in the European legal space—and how crucial judicial cooperation is in ensuring justice.
Unity of the European Legal Area and the Limits of National Prosecution
The CJEU’s decision underscores that the ne bis in idem principle in EU law must be interpreted substantively rather than formally. What matters is not the legal provisions applied but the underlying conduct. This strengthens protection against double jeopardy while requiring national courts to carefully examine cross-border cases.
For law enforcement, this means that close cooperation is essential to prevent individuals from being prosecuted multiple times for the same acts in different Member States. For defendants like MSIG, it ensures that they cannot be tried repeatedly for the same conduct under different legal classifications.
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