Ne Bis Interpretatio in Idem? The Two Faces of the Ne Bis in Idem Principle in the Case Law of the European Court of Justice

The meaning of idem in the ne bis in idem principle is controversial in the case law of the Court of Justice of the European Union. In interpreting the provision of Article 54 of the Convention Implementing the Schengen Agreement, the court has emphasized the necessary requirement in the identity of the material acts while in antitrust law three requirements have been deemed necessary: (1) Identity of the facts, (2) unity of offender, and (3) unity of the legal interest protected. Despite the opinions of some Advocates General, the court has confirmed different interpretations of the same principle, depending on differences of the legal scope in question. A few years ago, however, the European Court of Human Rights proclaimed the criterion based on the identity of the material acts as the most suitable. This might push the Court of Justice of the European Union to correct its position in the antitrust field. Should this happen, this adjustment might serve as grounds to recognize the existence of a regional custom concerning the ne bis in idem principle.