The Rome Statute of the International Criminal Court (ICC) entered into force on 1st July 2002 and included provisions granting the ICC jurisdiction over four core crimes: genocide, crimes against humanity, war crimes and the crime of aggression.  However, from the moment of inception, the ICC lacked the authority to prosecute crimes of aggression due to disagreements among state parties regarding a legal definition of the crime.
In order to deal with the many legal complexities that defining a Crime of Aggression entails, a Special Working Group on the Crime of Aggression (SWGCA) was established in 2002 to work on a definition and submit proposals for the Review Conference scheduled in 2010.
The purpose of prosecuting Crimes of Aggression is to hold accountable those who instigate and engage in unjustified armed conflicts between states.  This notion first emerged at the end of World War II when during the Nuremberg and Tokyo Trials it became evident that the absence of a general prohibition in international law against the waging of war could no longer be tolerated in a modern world.
Since then, many obstacles needed to be overcome to find international consensus on the issue. The legal definition consists of two parts; first, the elements that define when a crime of aggression has been committed, and second, the circumstances which give the ICC active jurisdiction over the crime. 
Another controversial issue in this matter is which international institution or body will be authorized to determine whether a crime of aggression has been committed. Article 39 of the UN Charter states that ‘ The Security Council shall determine the existence of any threat to the peace, breach of the peace, or act of aggression and shall make recommendations, or decide what measures shall be taken in accordance with Articles 41 and 42, to maintain or restore international peace and security. Article 13 of the ICC Statute states that the Security Council can refer a case to the ICC, enabling the ICC to exercise jurisdiction over a conflict even if the parties involved have not accepted the ICC’s jurisdiction. This means that the Security Council has already been granted considerable powers under the ICC Statute which can therefore be extended to the crime of aggression once the ICC’s jurisdiction over this provision becomes operational. However, many UN member states fear that the five permanent members of the Security Council will, through their veto powers, prevent the ICC from effectively prosecuting crimes of aggression and in doing so politicize international criminal legal proceedings. This would adversely affect the ICC’s legitimacy and run counter to the general principle that the law applies equally to all. 
Some legal scholars argue that the Security Council’s power to determine the existence of an act of aggression is not exclusive and that the UN Charter under Chapter VI permits other bodies such as the General Assembly or the International Court of Justice (ICJ) to determine the existence of aggression through an advisory opinion. Bringing in the ICJ would seem like an obvious choice as it is a judicial body and has in several cases made determinations regarding the unlawful use of force.  Another good reason for the ICC to seek an advisory opinion of the ICJ is to reduce the risk of inconsistencies or conflicts with decisions of the ICJ in ICC aggression cases. 
Although the First Review Conference of the Statute of Rome will not discus the role of the UN Security Council or the ICJ in ICC matters, it has nonetheless the potential to dramatically change the way in which the ICC will function in the future. Above anything else, it can be considered an opportunity to influence and improve the global struggle for human rights.
The Crime of Aggression before the First Review of the ICC Statute, by Claus Kress in Leiden Journal of International Law, 20 (2007), p. 862
 The Security Coun
cil, The International Criminal Court, and the Crime of Aggression; How Exclusive is the Security Council’s Power to Determine Aggression? by M.S. Stein in Indiana International and Comparative Law Review, 16 (1) p. 32-33, 2005