Following World War II, international human rights law and international criminal law began their modern development down parallel tracks. Their convergence is more recent.
On 26 June 1945, the United Nations Charter was signed in San Francisco, and the treaty entered into force the following October. The Charter, inter alia was meant “to save succeeding generations from the scourge of war . . . and to reaffirm faith in fundamental human rights, in the dignity and worth of the human person, in the equal rights of men and women and of nations large and small.” Although the Charter did not directly impose human rights obligations on state parties, it did oblige them to promote and respect “human rights and fundamental freedoms” and “to take joint and separate action in co-operation with” the UN to achieve that goal. A network of enforcement mechanisms developed over time, both directly based on the Charter (charter-based procedures) and through human rights treaties and their enforcement bodies (treaty-based bodies).
Meanwhile, the Allies, having prevailed in the war, established criminal trials for defeated German and Japanese military and civilian leaders, charging them crimes against peace, war crimes, and crimes against humanity. The first trial opened at the International Military Tribunal at Nuremberg on November 20, 1945, and the Tokyo War Crimes Tribunal convened its first military trial on April 29, 1946. Robert Jackson, who led the prosecution at Nuremberg, described the Allies’ choice to give the accused due process of law “one of the most significant tributes that Power has ever paid to Reason.” Both tribunals completed their work before the close of the decade, and the promise of international criminal law was largely – if temporarily – abandoned.
International human rights law has grown to become a robust, overlapping, and interconnected system of international, regional, and national guarantees and mechanisms that require states to respect the rights of individuals. The degree to which states are governed by human rights norms and procedures varies, however, according to their individual histories of ratification or accession to certain treaties or past compliance with customary international norms.
International human rights law as we know it today . . seeks to protect individual human beings without regard to their nationality or other status. That is its most distinguishing characteristic and overarching value.Thomas Buergenthal, The Evolving International Human Rights Law System, American Journal of International Law
Some human rights norms, referred to as peremptory or jus cogens norms, apply everywhere and are obligatory in all contexts. While there is no universal agreement as to the full list of jus cogens norms, it is generally accepted that these include the prohibitions on torture, genocide, piracy, slavery, and the slave trade. Violations of jus cogens norms constitute crimes for which states may be obliged to prosecute or extradite suspects, even in cases where the crimes were committed in the territory of another state.
International criminal law, by contrast with human rights law, comprises a narrow and largely parallel set of systems of international and national prohibitions and procedures designed to deter and punish individuals for certain categories of conduct. The core international crimes are genocide, war crimes, and crimes against humanity.
The wrongs which we seek to condemn and punish have been so calculated, so malignant, and so devastating, that civilization cannot tolerate their being ignored, because it cannot survive their being repeated.Justice Robert H. Jackson, Opening Statement before the International Military Tribunal
International criminal law institutions began a period of rapid development in the late twentieth century, and they did so largely within the framework of the United Nations Charter and in the pattern set by the international human rights treaty bodies. Thus, the United Nations charter-based procedures and international treaty bodies regularly interpret, incorporate, and build on developments in international criminal law. Although the criminal courts are obliged to develop jurisprudence with a focus on individual cases before them, in accordance with their mandates or national laws, they nonetheless may draw on human rights law sources in fashioning their opinions.
While Partners in Justice International centres its work on partnering with local practitioners seeking justice for international crimes (including jus cogens crimes) in national jurisdictions, opening pathways to justice for victims can often be enhanced by working through multinational or international institutions and initiatives.
 Thomas Buergenthal, The Evolving International Human Rights Law System, American Journal of International Law (2006) at 783.
 The 1969 and 1986 Vienna Conventions on the Law of Treaties specify that a treaty is void if it conflicts with jus cogens norms. See Vienna Convention on the Law of Treaties, arts. 53, 64. The International Law Commission adopted guiding principles in 2006 asserting that the same is true for unilateral declarations. Guiding Principles applicable to unilateral declarations of States capable of creating legal obligations, with commentaries thereto, United Nations International Law Commission, 58th Session, 2006.
 M. Cherif Bassiouni. (Autumn 1996) “International Crimes: ‘Jus Cogens’ and ‘Obligatio Erga Omnes’.” Law and Contemporary Problems. Vol. 59, No. 4, Pg. 68.