On March 20, 2018, the Grand Chamber of the Court of Justice of the European Union delivered a trio of judgments that substantially clarify the application of the ne bis in idem principle where both criminal and administrative proceedings are pursued. Both the Charter of Fundamental Rights of the European Union (the Charter) and the European Convention on Human Rights (ECHR) recognize the principle, but it will be more familiar to common law practitioners as the protection against double jeopardy. Increasingly, dual investigations are common in cases where the underlying activity is essentially financial crime, but tender areas continue to be information sharing and the risk of duplicate punishment where both investigations end in enforcement action. Concerning four cases, Case C-524/15 Menci, Case C-537/16 Garlsson Real Estate and Others, and joined Cases C-596/16 Di Puma and C-597/16 Zecca, each of the judgments addresses preliminary questions referred by the Italian courts; they are significant because they emphasize that ne bis in idem will not serve as a bar to a dual response. The interest in protecting the financial markets justifies limits to the principle but great care must be taken to coordinate the approaches and identify whether a further criminal sanction is masquerading as an administrative penalty.