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Directive 2014/41/EU of the European Parliament and of the Council of 3 April 2014 regarding the European Investigation Order in criminal matters

Preamble:
(17) The principle of ne bis in idem is a fundamental principle of law in the Union, as recognised by the Charter and developed by the case-law of the Court of Justice of the European Union. Therefore the executing authority should be entitled to refuse the execution of an EIO if its execution would be contrary to that principle. Given the preliminary nature of the proceedings underlying an EIO, its execution should not be subject to refusal where it is aimed to establish whether a possible conflict with the ne bis in idem principle exists, or where the issuing authority has provided assurances that the evidence transferred as a result of the execution of the EIO would not be used to prosecute or impose a sanction on a person whose case has been finally disposed of in another Member State for the same facts.
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Article 11. Grounds for non-recognition or non-execution:
1. Without prejudice to Article 1(4), recognition or execution of an EIO may be refused in the executing State where: ...
(d) the execution of the EIO would be contrary to the principle of ne bis in idem