Over the last few decades, a global trend of extending the reach of domestic penal power can be observed, namely driven by the changing face of crime as it becomes increasingly transnational in nature. It is demonstrated in this article that the Swiss legislature has clearly followed this global trend of broadening the extraterritorial reach of domestic criminal law, most notably since the 1980s. It has acted with particular resolve in the last decade, adding jurisdictional bases to the Swiss Criminal Code by virtue of which Swiss criminal law can be applied to many instances of conduct taking place abroad. Certain offences – specified crimes against minors and female genital mutilation – have even been subjected to an absolute and unrestricted universality principle. The Swiss legislature is not indifferent to the problems that such an expansive approach to jurisdiction may create, notably in terms of conflicts of jurisdiction. Yet, the rules it adopted to temper the effects of applying Swiss criminal law to extraterritorial conduct only partially remedy the situation. This development in Swiss law begs the question whether such an expansive approach towards jurisdiction is permissible – or even encouraged or requested by international law. Hence, this article explores to what extent international law informs the reach of domestic penal power and concludes that international law is Janus-faced with regard to the question of the geographical scope of domestic criminal law. While some of its rules push for long-arm jurisdiction, others put limits on the domestic legislature’s endeavour to expand the reach of its domestic criminal law. In light of this, the idea of adopting, on an international level, general principles governing the definition of the scope of domestic prescriptive and adjudicative jurisdiction for transnational cases is tempting, albeit difficult to realize.