Selective justice, judicial arbitrariness, uneven judicial practice and legal insecurity are among the multiple problems that create serious impediments in the reform of the criminal justice system in the Republic of Moldova. The resolution of the above-mentioned problems, which have started to become chronic for the national legal system, is conditional, including, on a good understanding and the effective functioning of the principle of criminal legality, both in the legislative work of developing criminal norms, and in the transposition activity of these norms in judicial practice. In European criminal law, criminal legality is a fundamental principle that ensures the legal protection of people against abuses by the authorities. Starting from these premises, the authors evaluated the degree of implementation of the legality of criminalization in the national criminal law system, highlighting findings and conclusions that we find useful for the sustainable development of regulations in the field of national criminal law.