The principle of "Nulla poena sine lege" is the most significant contribution of the enlightenment to the criminal law which emerged with the strengthening of human against the state, the recognition of the constitutional state based on human rights and restriction on the power of the administration and also is one of the fundamental principles of modern criminal law. This principle is the main solutions for the protection of fundamental rights and freedoms in the practice of criminal law which restricts the fundamental rights and freedoms most and is the most severe situation that people can face in social life and it is considered, for its mentioned feature, within the scope of "the guarantee function of criminal law". In this regard, it is observed that this principle has three functions; allowing the individual to know the limits of his freedom and direct his behaviours accordingly, preventing the arbitrary punishment and protecting the individual rights and freedoms against the political power, in other words against the executive body. According to the aforementioned principle, the acts constituting crime and the sentences to be imposed with regard to these acts are required to be governed by the normative texts drawn up by the legislative body and specified as "laws". Accordingly, as a result of the principle of nulla poena sine lege, "the principle of exclusivity of the laws" has been adopted with regard to the source of criminal law. This principle aims, unlike the sources of the laws generally, to restrict not the uncodified resources of criminal law, but the codified regulations except the laws , in other words to exclude the regulatory rules of the administration from the resources of criminal law and therefore to restrict the resources of criminal law with the laws. The issue which is dealt with the concept of "law" within the scope of the guarantee function of criminal law refers to legislative acts which are technically in the nature of laws with regard to the constitutional order. However, when criminal norms are considered, it may be observed that the principle of nulla poena sine lege is not implemented in a very strict way and, the executive body is granted, even if limited, some kind of power to define the crimes and set the punishments. While legislator sometimes does not define explicitly the act constituting crime, it grants the authority of defiinge to the administration within the specified framework and only sets the sanction to be implemented with regard to this act. In other words, granting the authority to define the scope of the prohibited acts, the legislator allows the administration to create the definition of the crimes. In doctrine, these are specified as "explicit, white or blind criminal codes". One of the most contradictive areas in Turkey with regard to the principle of nulla poena sine lege is the regulations giving the discretion of defining the crime and setting the punishment to the administration. It is a generally recognized fact that, with regard to constitution of a safe environment for the individual rights and freedoms, the principle of no crime and punishment without law is required to be implemented strictly. Besides, there are different opinions in the doctrine, as in the decisions of the Constitutional Court, concerning the issue whether defining crimes and setting punishments through the regulatory rules of the executive body violates the principle of legality. This article evaluates in details whether defining crimes and setting punishments through the regulatory rules of the executive body violates the principle of legality, taking into account the decisions of the Constitutional Court and the opinions set forth in the doctrine and it is tried to suggest solutions, in the framework of the discussions, for the problems encountered in this area.