In the modern world, the problems of criminalization and decriminalization remain one of the main aspects of Criminal Policy. The main problem is that criminal legislation should promptly react to changes in society, excluding actions that have lost public danger from the field of crime, and vice versa, be criminalized for new, socially harmful phenomena. To analyze modern trends in the field of criminalization and decriminalization, identify their consequences for law enforcement practice and give recommendations for improving legislation. In the course of the study, an analysis of criminal legal norms was carried out, domestic and foreign practices related to the processes of criminalization and decriminalization were considered in comparison. In addition, data and statistical data were used to assess the effectiveness of Legal Regulation. The study showed that it is important to take into account international experience. Decriminalization policies were positive in some countries and negative in others. For Kazakhstan, this study showed the need to adapt to modern challenges in the reform of criminal legislation, while maintaining national characteristics. The balanced conduct of criminalization and decriminalization not only increases the effectiveness of the law enforcement system, but also contributes to the strengthening of trust between the state and society. When implementing these processes, legislative decisions will have a positive effect only if they take into account public opinion, socio-economic factors and the capabilities of the legal system.