This paper addresses how the principle of ne bis in idem relates to the enforcement of EU competition law. Regulation 1/2003 came into force in 2004 and with this the enforcement system of EU competition law that had been in place for over 40 years was fundamentally reformed. Under the new modernized enforcement system of the EU competition rules, national competition authorities (NCAs) and national courts in the Member States share the power with the Commission to apply EU competition law. Regulation 1/2003 does not include rules on how the jurisdiction should be divided between the Commission, NCAs and national courts when applying the EU competition rules. As the Commission, NCAs and national courts all remains competent to deal with every infringement of the EU competition rules, the European Competition Network (ECN) was set up as a forum where the work of enforcing the EU competition rules could be divided between the Commission and the authorities in the Member States. The objective of the ECN is that each case that involves the application of EU competition law should be dealt by a single authority. However, there are no binding rules to guarantee that this will always be the case. Instead, the system of enforcement under Regulation 1/2003 allows for parallel or consecutive infringement proceedings and sanctions under the EU competition rules by more than one authority in the same case. As undertakings in the EU can be prosecuted more than once for the same anti-competitive behavior, the right of not being tried more than once for the same offence; the principle of ne bis in idem, is at risk of being violated. The principle of ne bis in idem is a fundamental human right guaranteed under all the different sources of human rights law recognized by the EU. The EU has reaffirmed its dedication to protecting human rights in the past several years. Since the Lisbon Treaty came into force in 2009, the EU formally recognizes three different sources of human rights law: The Charter of Fundamental Rights of the European Union, the European Convention for the Protection of Human Rights and Fundamental Freedoms and general principles as they result from the constitutional traditions common to the Member States. The protection of human rights in the Union legal order should therefore be far reaching. The increased protection of human rights in the EU means that when rules such as the enforcement rules of EU competition law are reformed, the protection of human rights need to be taken into account. The European Court of Justice (ECJ) also needs to assure that it provides for the widest protection of human rights possible by not interpreting the scope of human rights less extensively than the European Court of Human Rights (ECtHR).