This article analyses the application of the public interest in the reasoning of the Peruvian legislator for the decriminalization of crimes against honour. Dogmatic elements of a constitutional and criminal nature were taken into account on the normative provisions that protect honour against the illegitimate exercise of freedom of expression. This framework made it possible to analyse the conceptual content of the public interest in relation to freedom of expression. This is one of the most prominent criteria for the decriminalization of conduct that damages honour, where the dissemination of information and opinion are of special relevance for the deployment of the democratic process and fundamental rights in a constitutional State. In a first stage, the bills evaluated show a weak adherence to the role of the public interest to strengthen the deliberative premises of the democratic process. Nor did they adequately discuss the protected content of the right to honour and its protection through alternative means. These limitations improved in the most recent stage of the debate, which denotes a greater argumentative interest in the application of the public interest as a normative criterion to base decriminalization in accordance with the motivational duties of a rational legislator.