International criminal law (ICL) developed in large part from international humanitarian law during the mid-to-late twentieth century. The International Criminal Court (ICC), a permanent institution to investigate and prosecute ICL cases finally was established in 2002. Although widely supported, certain states feared that the ICC would diminish national sovereignty. Yet, in formal legal terms, ICL and the ICC’s Rome Statute are just like other branches of public international law in terms of their relationship with national constitutional arrangements. ICL does not challenge states’ primary executive and judicial powers; it does not introduce any general rights for citizens or particularly onerous obligations for states that are already subject to the rule of law; and its intrusion on national sovereignty is only in evidence when a state’s leaders either are responsible for atrocities or are incapable of protecting their citizens from such atrocities. ICL thus is very different from international human rights law (IHRL), which directly impacts national constitutional arrangements. When ICL does come into play, however, arguably it may perform quasi-constitutional functions, in particular offering the only means under public international law to remove state officials from office when they are believed responsible for the most harmful abuses of power.