This study deals with two aspects of international law. The first is ‘immunity of state officials’ and the second is ‘prosecution of international crimes.’ Immunity is discussed in the context of international crimes. The study focuses on Africa because African state officials have become subjects of international criminal justice before international courts and various national courts both in Europe and Africa. It presents a new contribution to international criminal justice in Africa by examining the practice on prosecution of international crimes in eleven African states: South Africa; Kenya; Senegal; Ethiopia; Burundi; Rwanda; DRC; Congo; Niger; Burkina Faso and Uganda. The study concludes that immunity of state officials has been outlawed in these states thereby rendering state officials amenable to criminal prosecution for international crimes. The thesis argues that although immunity is founded under customary international law, it does not prevail over international law jus cogens on the prosecution of international crimes because such jus cogens trumps immunity. It is argued that, committing international crimes cannot qualify as acts performed in official capacity for the purpose of upholding immunity of state officials. In principle, customary international law outlaws functional immunity in respect of international crimes. Hence, in relation to international crimes, state officials cannot benefit from immunity from prosecution or subpoenas. Further, the study criticises the African Union’s opposition to the prosecutions before the International Criminal Court (ICC). It argues that however strong it may be, such opposition is unfounded in international law and is motivated by African solidarity to weaken the role of the ICC in Africa. It concludes that the decisions taken by the African Union not to cooperate with the ICC are geared towards breaching international obligations on cooperation with the ICC. The study calls upon African states to respect their obligations under the Rome Statute and customary international law. It recommends that African states should cooperate with the ICC in the investigations and prosecution of persons responsible for international crimes in Africa. At international level, the study reveals the conflicting jurisprudence of international courts on subpoenas against state officials. It argues that, state officials are not immune from being subpoenaed to testify or adduce evidence before international courts. It contends that issuing subpoenas to state officials ensures fairness and equality of arms in the prosecution of international crimes. It recommends that international courts should treat state officials equally regarding prosecution and subpoenas. It further recommends that African states should respect their obligations arising from the Rome Statute and that, immunity should not be used to develop a culture of impunity for international crimes committed in Africa.