Ne Bis in Idem and International Judicial Cooperation in Criminal Matters: A Fragmented Guarantee in Search of a Unified Framework. A French Law Perspective

Abstract

The principle of ne bis in idem – that no person shall be tried or punished twice for the same offence – ranks among the foundational guarantees of criminal procedure. At the international level, however, it has no settled status. Long treated as a purely domestic rule, the principle’s traditional non-application between States has been progressively qualified by certain international conventions and by the statutes of the international criminal tribunals. Within the European Union, the transformation has been more ambitious: the principle has migrated from a domestic safeguard into a transnational fundamental right, constituting, by comparison with general international law, a genuinely European added value.

The analysis that follows is organised around a doctrinal distinction that the literature tends to elide : that between the res judicata effect of a foreign criminal judgment (autorité de chose jugée) –, whose negative expression is the ne bis in idem bar – and its enforceability (force exécutoire). It is argued that maintaining these two categories as analytically separate is the precondition for understanding both what the principle demands across cooperation mechanisms and where its limits lie.

On that doctrinal foundation, the article argues that the resulting guarantee is not a single rule but a system of five overlapping – and at times conflicting – regimes: the ordinary French domestic regime, subject to a territorial-jurisdiction exclusion; the ECHR Protocol No. 7 regime, confined to intra-State situations; the Schengen/Charter regime, genuinely transnational and recently extended to extradition to third States; the classic cooperation-treaty regime, structurally narrower; and the Interpol CCF regime, in which the principle operates at best as an administrative indicium. The article draws on the jurisprudence of the Court of Justice – from Gözütok and Van Esbroeck to HF (C-435/22 PPU) and Swiftair (C-701/23) – as well as that of the European Court of Human Rights, the French Court of Cassation, and the Interpol Commission for the Control of Files (hereinafter, the “CCF”), and on the newest developments in judicial cooperation, including the 2024 Transfer of Proceedings Regulation and the European Public Prosecutor’s Office, to map the principle across each layer of judicial cooperation and to identify the analytical variables that recur across all of them.

Three structural gaps emerge: the domestic/foreign sentence gap (only partially bridged by the Court of Cassation’s 2013 deduction rule and left open by the ongoing enforcement lacuna identified by Huet); the treaty gap exposed by HF; and the contractual blind spot left by the transnational circulation of DPAs and CJIPs. Alongside these gaps, two frontiers test the principle under maximum stress: corporate liability for atrocity crimes, illustrated by the Lafarge proceedings, and the investigative phase under the EIO and the European Public Prosecutor’s Office (EPPO). The article’s central claim is that the coherent application of ne bis in idem now demands a unified analytical framework – held together by the shared “certainty threshold” of C-505/19 – that neither the existing legislation nor the case law has yet supplied.