UNLAWFUL ACTS IN CRIMINAL ACTS (FORMAL AND MATERIAL APPROACH)

The development of contemporary criminal law reflects a growing tension between the formal legality principle and the material approach in defining crimes. Following the Constitutional Court Decision No. 003/PUU-IV/2006, the material approach gained constitutional legitimacy to accommodate substantive justice, which is often not fully captured within normative texts. This article aims to analyze the relevance and challenges of applying the material legality principle in the Indonesian criminal justice system, as well as to propose an integrative model that bridges the need for legal certainty (formal) with social justice (material). This study uses a normative juridical method with descriptive and comparative legal analysis based on legislation and jurisprudence. The findings indicate that the material approach has been selectively applied in narcotics cases, sexual violence, and cybercrime, although lacking systematic judicial guidelines. Therefore, an integrative model in legislation and judicial guidance is necessary to balance and control the responsible use of material legality. The conclusion emphasizes the urgency of harmonizing formal and material legality principles so that criminal law can be not only legally valid, but also socially just.