ENIn March 2019, the European Court of Human Rights issued its judgment in the case of Drėlingas v. Lithuania, concerning the application of the principle of legality with regard to the crime of genocide. The Court was called to review the compatibility of the conviction of Mr. Drėlingas – a senior official of the former Soviet Union’s state security agency who, in 1956, took part in an operation against Lithuanian partisans – with Article 7 of the European Convention on Human Rights. The applicant, indeed, lamented that Lithuanian courts sentenced him for being an ‘accessory to genocide’ by retroactively applying a wider notion of genocide, which had no basis in international law at the relevant time. The Strasbourg judges, eventually, found by majority that the conviction did not violate the principle of legality. This paper questions that Lithuanian partisans could have been considered as a part of the Lithuanian national group for the purpose of the crime of genocide, thus arguing that the Court erred in concluding that there was no violation of the Convention, with a possible far-reaching impact on future cases. Keywords: ethnopolitical genocide; principle of legality; substantiality of the part; Article 7 of the European Convention on Human Rights. [From the publication]