The ne bis in idem principle (prohibiting double jeopardy) is applied in various international instruments such as the General Data Protection Regulation (GDPR). Literally translated it means ‘not twice about the same’. In  principle nobody should be judged twice for the same “offence“. Historically, the principle derives from the Roman law maxim bis de eadem re ne sit actio.

“The ne bis in idem principle is included in many national, European and international legal instruments. Within the European Union’s area of Freedom, Security and Justice, the main legal sources are Articles 54 to 58 of the Convention Implementing the Schengen Agreement (“CISA”) and Article 50 of the Charter of Fundamental Rights of the European Union
(“Charter”). In general, the objective of the ne bis in idem principle is to ensure that no one is prosecuted for the same acts in several Member States on account of the fact that he exercises his right to freedom of movement (see infra Gözütok and Brügge, Gasparini).
The principle is also included as refusal ground in a large number of EU instruments on judicial cooperation in criminal matters, including mutual recognition instruments such as the
Framework Decision 2002/584/JHA on the European Arrest Warrant (“FD EAW”) and the Directive 2014/41/EU on the European investigation Order in criminal matters.
Moreover, the ne bis in idem principle is included in Article 4 of Protocol 7 to the European Convention on Human Rights (“Article 4P7 ECHR”)”.

The Principle of Ne Bis in Idem in Criminal Matters in the Case Law of the Court of Justice of the European Union