In proceedings in 2010 and 2011 the Norwegian Supreme Court dismissed a war crimes conviction under the relatively recently passed international crimes provisions of the Norwegian Penal Code. The Court held that the conviction was unconstitutional as it applied those provisions retroactively. This essay challenges that conclusion. The argument that this paper presents is that the Supreme Court’s decision is arguably untenable, inconsistent with the acknowledged obligations the state of Norway has long recognized it had (and are recognized under international law) to prosecute such acts as the international crimes they are and that in fact to do so is consistent rather than in contradiction any other than an absolutist originalist reading of the Norwegian Constitution. The precedential consequences of their decision are already being felt. On the 14 February 2013 a trial court convicted an accused for complicity in the Rwandan genocide. His conviction and the indictment were on the charge of murder, not genocide. Whilst there are different arguments with respect to other international crimes than those constituting grave breaches of the Geneva Conventions this paper argues that the rationale and conclusions reached by the Norwegian Supreme Court need to be revisited.