Case Law of the Court of Justice of The European Union on the Principle of Ne Bis In Idem

In order to implement ne bis in idem principle, which can be defined as the prohibition of reinvestigation, reprosecution and repunishment when there is a decision given against the same person for the same act, many factors must come together. It is possible to list these factors as criminal nature, same person, same act and a decision. From the point of the European Union, implementation of ne bis in idem is important because member states give validity to the decisions taken by other member states as if they were given by them. This is similar to the implementation in domestic law and it is also important to understand how the principle is implemented in international criminal law. For this reason, in this study, it is aimed to reveal the content of the elements of the principle of ne bis in idem by examining the decisions of the Court of Justice of the European Union. In the first part of our study the structure of the Court of Justice of the European Union will be examined in detail. In the second part, elements of ne bis in idem principle in international conventions and Turkish law will be discussed, in the third part, how the principle is interpreted by the European Union Court of Justice will be explained in comparison with the ECtHR decisions.