# The principle of ne bis in idem and the European arrest warrant as vehicles for the CJEU for redefining the powers of national prosecutions in EU law

## TL;DR

This paper explores how the CJEU's rulings on the ne bis in idem principle and the European arrest warrant have reshaped national prosecutions and criminal justice cooperation in the EU.

## Contribution

The paper reveals how CJEU jurisprudence redefines national prosecution powers and impacts EU-wide criminal justice harmonization.

## Key findings

- The CJEU's recognition of res iudicata effects of prosecutorial decisions enhances national prosecutions' authority.
- The CJEU's rulings elevate national prosecutions to a level akin to national courts in EU-wide criminal cooperation.
- These judgments may lower individual protections to facilitate smoother cross-border criminal justice cooperation.

## Abstract

The article examines how the Court of Justice of the European Union (CJEU) through its judgments enlarged the ambit of the ne bis in idem principle in a certain aspect and redefined attributes of national prosecutions. More poignantly, how the Court’s recognition of a possible res iudicata effect of prosecutorial decisions binding on other EU Member States triggering ne bis in idem protection not only empowered national prosecutions but also implicitly pushed Member States to further harmonize their criminal justice systems. At the same time, by finding that prosecutions may not only issue European arrest warrants (EAW) but also terminate criminal proceedings with res iudicata consequences obligatory for other Member States initiating EU wide recognition of the termination’s ne bis in idem force, the CJEU elevated national prosecutions—depending on domestic legal prerequisites—to the level of national courts. It is argued that by reading these judgments together, the CJEU’s jurisprudence might have created frictions between the Member States’ criminal justice systems and reshaped terms such as “judicial authority” and “effective judicial protection” in a way which lowers the level of protection afforded to the individual, be that, to make cooperation in criminal matters more effective between Member States.