The paper is devoted to an actual problem of the legal theory and practice, namely: the institution of circumstances excluding criminal nature (criminality) of an act (Chapter 8 of the Russian Criminal Code). As a manifestation of criminal and legal compromise steadily strengthening its position in domestic criminal legislation, this legal phenomenon is intended to encourage citizens to commit actions that contribute to localization or minimization of threats to the interests of the individual, society and the state protected by the law. At the same time, despite seemingly clear legislative enactment, the institution of circumstances precluding the criminal nature of an act evokes hot scientific debates. Among forensic scientists there is no uniform opinion concerning the legal nature of the criminal law institution as a whole and some of the individual types of circumstances constituting the institution under consideration, in particular. The legal literature substantiates the idea of the need to expand the legislative list of such circumstances. Investigators and judges often face difficulties in practical application of the rules enshrined in articles of Chapter 8 of the Criminal Code (especially provisions concerning necessary defense, extreme necessity, reasonable risk). The reasons for theoretical and practical problems related to the circumstances excluding the criminal nature of the act are largely preconditioned by the insufficient research of the institution under consideration in the general theory of law. This fundamental theoretical legal science lacks general legal equivalents of the criminal law concepts “criminality of the act”, “circumstances excluding criminality of the act.” It is proposed to introduce into scientific circulation the general legal equivalent of the concept “criminality of the act” — “delinquency of the act”, representing the set of such features of the offense as public harm, wrongfulness, culpability and punishability. This new legal design will allow us to investigate the phenomenon of circumstances excluding criminality of the act in the light of a general theory of law, to determine the possibility and limits of their subsidiary application in various branches of law. Thus, categories of circumstances excluding criminal, administrative, civil. disciplinary delinquency of acts will acquire the right to exist in differnt legal sciences and relevant branches of law. This, in turn, will contribute to improving the effectiveness of protection of rights, freedoms and legitimate interests of the individual, ensuring the interests of the society and the state.