In a ruling of 17 September 2009 the European Court of Human Rights has reinterpreted Article 7 of the European Convention on Human Rights (ECHR). The two most important issues in the Court's judgment are whether a provision of a Code of Criminal Procedure may be categorised as a “penalty” in the sense of Article 7, and whether Article 7 guarantees the lex mitior principle (providing for the applicability of the more lenient law). Focus is particularly placed on the outcome and implications of the Court's reinterpretation of Article 7 ECHR to include the lex mitior principle. Arguably, in the case of Scoppola v. Italy, the Court recognised both parts of the principle (the constitution of the criminal off ence and the imposition of the penalty). This article argues that the lex mitior principle should not have been included in the Convention by interpretation. Furthermore, it demonstrates that reinterpretation of the part of the principle concerning the constitution of the criminal offence is inconsiderate and may lead to inappropriate results.