In the last decade, it has become increasingly common for Swedish courts to try so-called international crimes - i.e. serious violations of international law that otherwise often go unpunished. These have included war crimes and genocide linked to conflict zones in different parts of the world. In the future, it is very likely that we in Sweden will see convictions for acts committed in the context of Russia's war in Ukraine. These international crimes are rooted in international law dating back to the aftermath of the Second World War. Since 2002, these crimes can be investigated and tried by the International Criminal Court in The Hague. Nowadays, however, the vast majority of prosecutions take place in courts in different national legal systems. When interpreting Swedish criminal provisions, international law standards need to be taken into account. This is material that is otherwise foreign to criminal law and is found in sources outside the Swedish legal system. One question that arises is how this material should be delimited; to what extent Swedish or international rules should be applied when assessing responsibility for the crimes. Furthermore, it is important that this difficult-to-understand material is systematized and made available to legal practitioners. The research project aims to investigate the above-mentioned issues and contribute to further knowledge regarding how the provisions should be interpreted and applied, which would contribute to facilitating the enforcement of liability for these very serious crimes as well as to a more legally secure and uniform application of the law.