As noted above, by the time that the Rome Statute entered into force in July 2002, the United States declined to exercise its right to participate as an observer in the Assembly of States Parties (ASP). It also eschewed meetings of the Special Working Group on the Crime of Aggression convened by the ASP to develop proposed amendments to the Rome Statute on the crime of aggression. Specifically, from 2003 to 2009, the Special Working Group periodically met and reported to the ASP on its progress on proposed amendments to be considered at a future Review Conference to define the crime of aggression and set out the conditions under which the Court would be able to exercise jurisdiction over the crime. In the absence of the United States, states eventually agreed on a package that, while ostensibly based on the principle that “nothing was decided until everything was decided,” in fact represented consensus on all but two issues: the role of the Security Council and how the amendments would enter into force.
When the Obama Administration took office, the United States reengaged on these issues. Obama Administration officials concluded that, in addition to its strong interests in the two pending issues, it saw deep flaws in the definition on which the Special Working Group had reached consensus. For their part, however, the participating states were understandably unwilling to reopen the text upon which they had agreed after seven years of painstaking negotiations from which the United States had absented itself. Those involved in the process believe there is little doubt that the definition would have avoided these flaws if the United States had participated in the negotiations and made its views known.
The United States then embarked upon extensive diplomatic efforts to address its concerns, including by sending a large interagency delegation, with representatives from Congress as public members, to the Review Conference held in Kampala, Uganda, in 2010. Despite the fact that the wording of the definition was treated as “locked,” the United States persuaded the states parties to adopt a series of “Understandings” regarding how the definition would be interpreted, such as identifying thresholds for a finding of aggression. Even more importantly, the final package included provisions that prevent the Court from exercising jurisdiction over the crime of aggression with respect to United States nationals. In the end, the United States engagement resulted in the adoption of a set of amendments that were highly protective of United States interests. As summarized in a bipartisan Senate Foreign Relations Committee staff report, active U.S. participation at the Kampala Conference played a crucial role in securing these protections:
“Absent U.S. participation and engagement before and during the Kampala Conference, it is unlikely that the conference would have specifically exempted non-ICC parties from key portions of the proposed aggression regime. It is also unlikely that the conference would have adopted understandings to address ambiguities in aspects of the definition of aggression.”
In addition, the United States participated actively at Kampala on other issues of significant concern to both the Defense and State Departments, and was able to secure language to ensure that amendments to the Rome Statute’s definition of war crimes aligned with U.S. views on international humanitarian law and that U.S. nationals would not be subject to the Court’s jurisdiction for conduct covered by the amendments. The United States was also the only non-member state to engage in the pledging exercise conducted in connection with the Review Conference, with a pledge to, among other things, “support efforts to bring the [Lord’s Resistance Army’s] leadership to justice” along with rule of law and capacity-building projects to enhance states' abilities to hold accountable those responsible for international crimes.