Horizontal Complementarity

Abstract

This chapter tackles the question whether a subsidiarity/complementarity principle – as is set out in Article 17 of the Rome Statute of the International Criminal Court – governs domestic prosecutions for international crimes on the basis of universal jurisdiction (a ‘horizontal’ complementarity principle): are ‘bystander’ states that have no link with those crimes but nevertheless want to prosecute them required to defer to states that have a stronger link and that are able and willing to investigate and prosecute? The author derives from a discussion of six relevant elements of the international legal system that there is no strong legal requirement of horizontal complementarity. Nevertheless, it amounts to proper criminal policy to defer to ‘territorial’ states (states on the territory of which the crime has been committed) that intend to embark in good faith on their own investigations and prosecutions.