Few issues in international criminal law are the subject of such intense discussion and controversy in legal literature and case law as the Joint Criminal Enterprise (JCE) and alternative forms of liability in international criminal law. The focus of legal literature and case law has long been on the JCE doctrine. Part A of this thesis gives an insight into the background, circumstances, difficulties, and preconditions of individual responsibility in collective crimes, and it highlights the development of the JCE doctrine and its background. However, since the International Criminal Court (ICC) has rejected JCE for the time being, the current discussion focuses on alternative forms of liability. This study aims at bringing JCE back into play by proposing a redefinition of the fundamental elements of JCE. Part B provides a detailed analysis of the objective and subjective elements of JCE that uncovers imprecise definitions and shortcomings in the elements of JCE. This section presents a revisited version of JCE that addresses the criticism of the concept. Part C deals with the forms of liability applied by the ICC for defining individual criminal responsibility in system criminality. It discusses the advantages and disadvantages of these alternatives to the JCE doctrine and compares the possible forms of liability and their elements - including the JCE. Furthermore, it assigns all these forms of liability to typical categories of cases, and it proposes a diversified approach that suggests not just focusing on one form of liability but defining several forms of liability depending on the involved protagonists and hierarchical levels in a particular situation. Part C is an exploratory dogmatic analysis of the underlying factual constellations of possible forms of liability, as well as the interferences between these forms and constellations. The main question asked is if JCE is essential as one of several forms of liability and is indispensable when it comes to dealing with the various factual constellations of collective and systemic criminality. Thesis. (Series: Volkerstrafrecht und Internationales Strafrecht) Subject: International Law, Criminal Law]