One of the unique challenges that the International Criminal Court's (ICC's) Office of the Prosecutor (OTP) faces is deciding when and where to launch investigations. It is a task that other international prosecutors have not confronted. Their investigative “situations” were selected in advance, leaving those prosecutors free to focus on the myriad other challenges any international justice enterprise faces. The ICC prosecutor's ability to define her own investigative situations (within the limits of jurisdiction) is both a boon and a burden. On the one hand, it accords the OTP the freedom to select the situations it deems most serious and worthy of international attention. Yet this discretion can also generate intense strain for the prosecutor of a still novel and fragile institution.

On March 9, 2018, the highest officials of the International Criminal Court (ICC) and representatives of the international community assembled at the seat of the Court to welcome six newly elected judges and to bid farewell to the six who had concluded their term of office, including myself. In my then-capacity as President, I presided over their swearing-in ceremony, which, in accordance with the Rome Statute, must take place in open court. In my opening remarks, I emphasized that this ceremony, which takes place every three years, was an important moment for the institution. Six new judges were solemnly undertaking to exercise their respective functions impartially and conscientiously, something that embodies both individual and collective responsibilities. “Through renewal,” I said, “the institution ensures its continuity.”

In a world in which war crimes, crimes against humanity, and genocide are not uncommon, the institution that was set up to have jurisdiction over them is in danger of being unable to discharge its mandate. Put starkly, the International Criminal Court (ICC) suffers too frequently from an inability to arrest or otherwise detain alleged perpetrators, whether the prosecutor is acting proprio motu or is following a reference to the court by a state party or the Security Council. The situation of Saif al-Islam Gaddafi is a case in point: notwithstanding the Security Council's referral of Libya to the ICC, at least as a member of the public it is difficult to detect any substantial international pressure that has been applied to have Gaddafi transferred to the Court; instead, he has been mooted as a candidate in future presidential elections. In total, the Court has issued thirty-two arrest warrants and nine summonses to appear, yet has held only nine individuals in custody, with fifteen still at large. The fugitives include citizens of the Democratic Republic of Congo, Uganda, Sudan, Kenya, Libya, and the Ivory Coast. Once the present trials before the court have concluded, there is only one case potentially waiting in the wings. A sole outstanding individual, Al-Hassan Ag Abdoul Aziz Ag Mohamed Ag Mahmoud from Mali, has made an initial appearance, and later this year the pre-trial stage of his case should commence; otherwise, there are simply the three trials in progress. However, I urge careful reflection before the Court is blamed for periods in which its docket of cases is lean.

More than any other international criminal tribunal, the International Criminal Court (ICC) has, in its early years, pursued cases against heads of state. The Court issued arrest warrants for President Omar al Bashir of Sudan and for Muammar Gaddafi while he was Libya's head of state, and it charged Uhuru Kenyatta shortly before he became head of state of Kenya. These attempts to prosecute heads of states have not only led to tensions between the Court and the African Union,1 but also pit the desire to hold senior leaders accountable for grave international crimes against the customary international law principle that certain senior state officials—especially heads of state—have immunity from foreign criminal jurisdiction by virtue of their status, including immunity from arrest and their inviolability when abroad.2

When it was adopted in 1998, the Rome Statute of the International Criminal Court (ICC) represented a significant breakthrough regarding sexual and gender-based crimes—crimes that, for centuries, had proliferated in armed conflicts but had been disregarded, mischaracterized, or misunderstood as the inevitable by-products of war or a legitimate part of its spoils. Not only did the Rome Statute explicitly treat a broad range of sexual acts as crimes against humanity and war crimes, but it also recognized gender-based violence as a crime and incorporated a number of provisions aimed at ensuring greater institutional attention to sexual and gender-based crimes. However, abstract possibilities do not always translate into concrete results, and the ICC has been slow to effectuate its innovative statutory provisions. This essay will explore some of the obstacles encountered and opportunities missed by the Court over the last twenty years, as well as highlighting welcome strides made in recent years to fulfill, at least in part, the promise of Rome.

Article 21 of the Rome Statute, in defining the applicable sources of law for the International Criminal Court (ICC), breaks with the practice of the ad hoc tribunals by treating customary international law as only a secondary authority. Nonetheless, customary international law still has an acknowledged role in ICC jurisprudence in filling lacunae in the Rome Statute and aiding in its interpretation. One can also predict other instances in which the application of customary international law will be required. It remains to be seen, however, whether the ICC's use of customary law will lead to that law's further fragmentation or whether that use will instead modify customary law to reflect the ICC Statute.