Stuck in Between

What happens when the International Criminal Court (ICC) concludes that the legal threshold for opening an investigation has been met, yet declines to take the procedural step required to initiate one? The recent memorandum of understanding (MoU) between the ICC and Nigeria, which effectively defers to Nigeria’s primary responsibility to address alleged crimes under ICC jurisdiction, raises that question in stark terms. This article argues that while complementarity remains a cornerstone of the Rome Statute system, it cannot justify the emergence of a procedural middle ground that displaces judicial oversight, prolongs uncertainty for victims, and weakens the coherence of international criminal law.

Introduction

In March 2026, the Deputy Prosecutor of the ICC concluded an official mission to Nigeria with the signing of an MoU intended to strengthen cooperation and support domestic accountability efforts. On its face, the development appears consistent with Article 1 of the Rome Statute, which establishes the Court as “complementary to national criminal jurisdictions.” There is nothing inherently objectionable about encouraging states to investigate and prosecute international crimes themselves. The difficulty lies elsewhere.

The Nigeria situation had already undergone a decade-long preliminary examination. In December 2020, the Office of the Prosecutor concluded that there was a reasonable basis to believe that war crimes and crimes against humanity had been committed by both Boko Haram and elements of the Nigerian security forces during the conflict in north-east Nigeria. The conflict, which began in 2009, has resulted in tens of thousands of deaths, mass displacement, and widespread allegations of atrocities by both insurgent groups and state actors. Although Nigeria has conducted numerous trials of alleged Boko Haram members, concerns persist that accountability efforts have largely focused on low-level perpetrators.

Under Article 15(3) of the Rome Statute, once the Prosecutor concludes that there is a reasonable basis to proceed, he or she “shall” seek authorisation from the Pre-Trial Chamber. Yet no investigation has been opened. This post argues that Nigeria now occupies a non-statutory space between preliminary examination and investigation, creating what may best be described as complementarity by suspension.

The Statutory Architecture of Complementarity

Complementarity is not a mere policy preference, it is built into the structure of the Rome Statute. Article 17(1)(a) provides that a case is inadmissible where it “is being investigated or prosecuted by a State which has jurisdiction over it,” unless that State is “unwilling or unable genuinely to carry out the investigation or prosecution.” The Statute, therefore, does not ask whether a state has performed accountability in the abstract. It asks whether there are genuine proceedings in relation to the relevant case. This distinction matters because the existence of domestic trials does not automatically displace ICC jurisdiction. The trials must concern substantially the same conduct and the same persons or categories of persons that would otherwise fall within the Court’s investigative focus. Article 17(2) further provides that unwillingness may be inferred where domestic proceedings are undertaken for the purpose of shielding a person from criminal responsibility, where there has been an unjustified delay inconsistent with an intent to bring the person concerned to justice, or where proceedings are not being conducted independently or impartially. These provisions make clear that complementarity is not satisfied by movement alone. It is satisfied by genuine accountability.

Scholars have long warned against confusing the doctrine with deference. William Burke-White’s account of proactive complementarity emphasised the potential for the ICC to catalyse domestic proceedings rather than simply replace national courts. Carsten Stahn distinguished between complementarity as a rule of admissibility and complementarity as a broader policy of cooperation. Darryl Robinson, writing on the conceptual complexity of complementarity, showed that the doctrine is often asked to perform too many functions at once: jurisdictional allocation, legitimacy management, institutional restraint, and political reassurance. These insights remain useful for Nigeria. They help us see that the present problem is not the OTP’s interest in domestic accountability. The problem is whether policy complementarity is being used to suspend legal complementarity.

Nigeria and the Problem of Selective Domestic Accountability

The Nigeria situation presents precisely the kind of case for which complementarity was designed, but also the kind of case in which it can be most easily misused. The conflict in north-east Nigeria has generated allegations of grave crimes by insurgent groups and by state forces. The Nigerian authorities have conducted mass trials of persons alleged to be associated with Boko Haram. Yet the central complementarity question is not whether Nigeria has prosecuted some suspects. It is whether Nigeria has genuinely investigated and prosecuted those most responsible for the full range of alleged crimes, including crimes attributed to state actors.

The distinction between low-level prosecutions and responsibility-bearing prosecutions is essential to international criminal law. The ICC is not designed to prosecute every suspect. It is concerned with those who bear the greatest responsibility for the most serious crimes of concern to the international community. Where a state prosecutes only foot soldiers, detainees, or marginal participants while leaving senior commanders and state agents untouched, complementarity cannot be presumed. Indeed, such proceedings may produce the appearance of accountability while leaving intact the structures of impunity that made the crimes possible.

This is where Nigeria becomes doctrinally significant. The OTP’s 2020 assessment recognised that domestic proceedings had not sufficiently addressed allegations against members of the Nigerian security forces. The subsequent turn to a memorandum of understanding must therefore be evaluated against that background. If the same factual and legal concerns remain, then the MoU cannot by itself cure the admissibility problem. A cooperation agreement may support complementarity, but it cannot substitute for genuine proceedings. Nor can diplomatic engagement erase the statutory consequences of a finding that the Article 15 threshold has been met.

Complementarity, Delay, and the Risk of Procedural Evasion

The Nigeria situation exposes a deeper challenge within the Rome Statute system: how to balance complementarity with the need to ensure justice for victims where the state appears to be unwilling or unable to investigate or prosecute. Article 15 was designed precisely for this purpose. It allows the Prosecutor to initiate investigations proprio motu, but subjects that power to judicial oversight by requiring authorisation from the Pre-Trial Chamber once the Prosecutor concludes that there is a reasonable basis to proceed. This framework ensures that neither prosecutorial paralysis nor unilateralism from the OTP prevails. Yet the current approach appears to leave Nigeria in a procedural limbo. Having concluded in 2020 that the threshold for investigation had been met, the Office of the Prosecutor has neither sought judicial authorisation nor formally closed the matter. The result is a situation in which prosecutorial control continues without meaningful judicial scrutiny, creating an accountability gap that sits uneasily with the structure of the Rome Statute.

The Office may defend its approach as an exercise in positive complementarity in line with its 2013 Policy Paper on Preliminary Examination. In principle, there is much to commend in encouraging national authorities to investigate and prosecute international crimes themselves. The ICC was never intended to prosecute every atrocity case, and domestic accountability remains the preferred outcome under the Rome Statute. However, complementarity has limits. It cannot override statutory requirements or transform a mandatory procedural step into an indefinite diplomatic process. Nor can it equate promises of future accountability with genuine present action. As scholars have long observed, complementarity carries a potential “shadow side”: states may engage in selective prosecutions, establish investigative mechanisms, or enter into cooperation arrangements that create the appearance of progress while avoiding politically sensitive cases involving those most responsible. In such circumstances, the Court must look beyond formal activity and assess whether domestic proceedings are genuinely capable of delivering meaningful accountability.

Ultimately, the consequences of this uncertainty are borne by victims. For communities affected by atrocities in north-east Nigeria, more than fifteen years have passed since the conflict generated allegations of war crimes and crimes against humanity on a significant scale. Many have already endured cycles of violence, displacement, failed domestic accountability efforts, and a decade-long ICC preliminary examination. To now be told that the situation remains under cooperative assessment without a clear legal timetable risks undermining confidence in the very system that was designed to provide a measure of justice when national systems fail. Delay is not a neutral phenomenon. Evidence deteriorates, witnesses disappear, memories fade, and the prospect of accountability becomes more remote. International criminal law derives much of its legitimacy from the promise that grave crimes will not simply be forgotten. Where a finding that the threshold for investigation has been met is followed by years of procedural uncertainty, the danger is that complementarity ceases to function as a mechanism for accountability and begins to resemble a vehicle for its indefinite postponement.

Regional Complementarity, the Malabo Protocol and the African Accountability Question

The Nigeria situation also speaks to a broader African debate about the future of international criminal justice. While many African states were instrumental in establishing the Rome Statute system, concerns about selectivity, unequal enforcement, and geopolitical imbalance have continued to shape the continent’s relationship with the ICC. The answer to these concerns cannot be the abandonment of international criminal law, nor can it be the assumption that accountability must always be delivered from The Hague. Rather, the future of atrocity accountability is likely to be multi-layered, involving domestic courts, regional institutions, hybrid mechanisms, and international tribunals operating within a broader ecology of justice.

This vision finds its clearest expression in the Malabo Protocol, adopted by the African Union in 2014. The Protocol seeks to establish a criminal chamber within the African Court of Justice and Human and Peoples’ Rights with jurisdiction over genocide, crimes against humanity, war crimes, unconstitutional changes of government, corruption, and other serious transnational crimes. Yet more than a decade later, the Protocol remains far from entering into force, with ratifications still well below the fifteen required. The result is a striking paradox: Africa possesses perhaps the world’s most ambitious regional criminal justice blueprint, yet the institution itself remains dormant.

Whether the Malabo Protocol remains a viable political project or has become largely aspirational remains uncertain. Nigeria has become an important test case. If the ICC-Nigeria memorandum produces credible investigations and prosecutions, complementarity may be vindicated. If it produces only delay and selective accountability, it will strengthen the case for regional complementarity and the operationalisation of the Malabo Court. Regional complementarity is not a retreat from international criminal law or a justification for impunity. Its purpose is to expand accountability by creating additional forums through which justice can be pursued when national systems fail. Any future regional mechanism will ultimately be judged by its willingness to hold both state and non-state actors accountable, regardless of rank or political influence.

Not a Conclusion

The ICC’s approach to Nigeria exposes a serious tension within the Rome Statute system. Complementarity is intended to ensure that states take primary responsibility for prosecuting international crimes, while preserving ICC intervention where domestic justice fails. Yet there is a danger that it can become a shield behind which accountability is indefinitely deferred. The memorandum between the OTP and Nigeria may yet produce genuine domestic prosecutions, but it does not resolve the legal question arising from the OTP’s 2020 conclusion that the threshold for opening an investigation had been met. If Article 15(3) of the Rome Statute imposes a duty to seek authorisation from the Pre-Trial Chamber, prolonged diplomatic engagement cannot substitute for the procedure prescribed by the Statute. The ICC should therefore clarify the legal basis of its current position and establish transparent benchmarks, timelines, and reporting obligations. If Nigeria demonstrates a genuine willingness and ability to prosecute those most responsible, complementarity will have achieved its purpose. If not, the Prosecutor should proceed under Article 15. The implications extend far beyond Nigeria. If cooperation and selective domestic action become sufficient to postpone ICC investigations indefinitely, complementarity risks evolving from a doctrine of shared responsibility into one of negotiated impunity.