The article examines extradition as a criminal-law mechanism for implementing the principle of the inevitability of criminal liability in the context of the growing transnational nature of crime and the expansion of international cooperation between states. It is argued that although extradition is traditionally classified within international and criminal procedural law, it possesses a distinct criminal-law dimension, as it is directly related to the extraterritorial application of criminal law and the enforcement of criminal responsibility. The study analyzes the criminal-law grounds of extradition, including the principle of double criminality, the seriousness of the offense, limitation periods, and other factors determining the admissibility of surrender. Particular attention is paid to the relationship between extradition and alternative forms of exercising criminal jurisdiction, as well as its role in preventing the evasion of criminal liability through cross-border movement. The article concludes that extradition serves as an essential instrument for ensuring the inevitability of criminal responsibility and enhances the effectiveness of criminal-law protection. Proposals are formulated for further theoretical development of extradition within the system of criminal law.