A Trailblazer for the Complementarity: Iraq, the UK Armed Forces, and the International Criminal Court

The ‘situation’ between Iraq and the UK had long been under the scrutiny of the International Criminal Court (ICC). As early as 2004, the Office of the Prosecutor (OTP) received communications from individuals and NGO’s – as Amnesty International and Human Rights Watch –, regarding the launching of military operations and the resulting human loss in Iraq, and therefore a preliminary examination into Iraq/UK situation was opened. On 09 February 2006, the former ICC Prosecutor Luis Moreno-Ocampo, after having analysed over 240 communications, information and divergent sources documentation, in accordance with the proprio motu powers under Article 15 of the Rome Statute, announced the closure of the preliminary examination into the Iraq/UK situation. As Moreno-Ocampo explained in his letter to these groups, the reasoning for the closure was that the required “gravity” threshold of Article 17 of the Rome Statute was not met, since isolated war crimes with a small-scale number of victims are not sufficiently grave to be admissible under the ICC statutory law.

On 10 January 2014, the OTP received a new communication from ECCHR and PIL, entitled “Responsibility of Officials of the United Kingdom for War Crimes Involving Systematic Detainee Abuse in Iraq from 2003-2008.” In response, on 13 May 2014, Moreno-Ocampo’s successor, Fatou Bensouda, re-opened the preliminary examination. Since then, the OTP has received a total of 236 communications or additional submissions pursuant to Article 15 of the Rome Statute (par. 14 Final Report, hereinafter also “report”). The hopes of the advocacy groups that this would lead to a different outcome did not, however, materialize. On 09 December 2020 Bensouda decided to close the preliminary examination for the second time the reasons for which are comprehensively explained in her report.

This post will consider three procedural aspects of ICC practice highlighted by the Iraq/UK inquiry and how this inquiry highlights the critical importance of the principle of complementarity. Specifically, it will include: 1) the alleged war crimes and the issues of jurisdictions; 2) issues of admissibility; 3) the complementarity in the light of the UK’s military and national investigations.

The alleged war crimes and the issues of jurisdictions

The detailed history of the Iraq/UK situation before the ICC is comprehensively documented in the Final Report published by the OTP on 09 December 2020. Based on that Report, the following issues of jurisdiction: ratione materiae; ratione temporis; ratione personae; ratione loci; are important to summarize.

For the jurisdiction ratione materiae, in Final Report (para. 2, 14-21, 46-53, 75-114) the Prosecutor indicated that jurisdiction ratione materiae imposed no impediment to seeking an investigation. Specifically, she concluded that alleged war crimes under Article 8 of the Rome Statute were presumably committed.

The Prosecutor reached a similar conclusion in respect to jurisdiction ratione temporis. The UK have deposited its instrument of ratification to the Rome Statute on 4 October 2001, therefore the ICC may exercise its jurisdiction from 1 July 2002 onwards (see Final Report para. 69-74).

Nor did jurisdiction ratione personae present any impediment to jurisdiction. Members of the UK armed forces are citizens of the UK.

With respect to jurisdiction ratione loci, it is important to highlight that since Iraq is not a State Party to the Rome Statute – and furthermore, Iraq has not lodged a declaration under Article 12(3) accepting the exercise of jurisdiction – not all the alleged crimes occurring on the territory of Iraq could properly be examined. Instead, only those involving UK members fell within the proper scope of the OTPs assessment (see Final Report para. 35-68). In other words, because the ICC does not have territorial jurisdiction in Iraq on the basis of article 12(2)(a), the preliminary examination had to be “necessarily limited” to the conduct of nationals of States Parties in Iraq, which is in this case was the UK, with respect to article 12(2)(b).

Based on these considerations, there were no jurisdictional impediments to requesting an investigation. Hence, the ‘key’ to understanding the decision of both Prosecutors is therefore not an abstract understanding of the Court’s jurisdiction, but the equally important consideration of admissibility.

Issues of admissibility

As indicated in article 53(1)(b) of the Statute (applied via rule 48 of the Rules of Procedure and Evidence (“Rules”), determining whether there is a “reasonable basis to proceed” to an investigation the Prosecutor shall consider whether “the case is or would be admissible under Article 17”.

Admissibility considerations are set out in Article 17 of the Rome Statute: “gravity” pursuant to Article 17(1)(d) and “complementarity” pursuant to Article 17(1)(a)-(c).

The “gravity” assessment (Final Report para. 119-127) was made by an evaluation of the following criteria, all of which satisfied the Prosecutor that further action was justified:  A) Scale of the crimes: (para. 128-133); B) Nature of the crimes (para. 134-139); C) Manner of commission (para. 140-144); D) Impact: (para. 145-148).

Thus, the outcome of this second assessment highlights what the State Parties to the Rome Statute expected would be a critical check on the exercise of ICC jurisdiction: complementarity.

The complementarity principle is contained in paragraph 10 of the Rome Statute Preamble, as well as in Articles 1 and 17(1)(a)-(c). This principle seems to permeate the entire structure of the ICC and is central to the intended role of the Court. Pursuant to the Rome Statute, ICC jurisdiction is never primary, but always only complementary to national criminal jurisdiction.

The thorough analysis of complementarity

The prosecutor engaged in a comparative analysis in order to implement the mandate of Article 17, essentially dividing the analysis into two parts following the so-called “complementarity test” inherited from a blend of the jurisprudence of the ICC derived from the cases of Lybia, Afghanistan, and Congo. These two steps are: 1) Verification of whether national authorities are active or inactive in relation to the same case; 2) If they are not active, assessment of whether this inactivity is the result of unwillingness or inability of the authorities to pursue a credible investigation and prosecution of the offenses.

In the ‘first step’ assessment, the Prosecutor analyzed the state of UK enquiries, investigations and prosecutions of the alleged crimes. Her report on this step is divided into many parts addressing, inter alia: the Institutional Mechanism: (see para. 159-162); the Iraq Historic Allegations Team: (see para. 163-181); the Service Policy Legacy Investigations: see para. 182-191); the Service Prosecuting Authority: (see para. 192-204). Moreover, the OTP analysed some of individual cases (para. 205-229) and the non-criminal mechanism (para. 248-274), as the “Iraq Fatality Investigations” (IFI), the “Systemic Issues Working Group” (‘SIWG’) or, in general, public inquiries and civil proceedings.  After having assessed the totality of this information the Prosecutor quit logically concluded that UK authorities had not been inactive (para. 275-279).

In the second step of her complementarity assessment, the Prosecutor evaluated UK investigation and prosecutorial efforts and decisions in terms of “genuineness (para. 280-491). These criteria are to be found in article 17(2), namely: the “intent to shield” (17(2)(a); the “unjustified delay” (17(2)(b); the “lack of independence or impartiality” (17(2)(c).

The Prosecutor concluded that the information assessed did not justify a finding of “shielding.” Nonetheless, the Report also indicated that she found, “deficiencies of the domestic processes that, while falling short of the threshold of establishing shielding, nonetheless give rise to the concerns in this report” (par. 490). Ultimately, however, this was insufficient to reach the admissibility in view of complementarity.

Conclusion: the Iraq/UK as a milestone of the complementarity

The OTPs second assessment was certainly a ‘win’ for the complementarity principle.

With all the other proverbial doors to the exercise of ICC jurisdiction opened, it was this last door that could not be unlocked. This is a positive outcome. Complementarity should be an important consideration of jurisdictional constraint at the earliest state of ICC inquiry in order to forego the cost and anxiety inflicted by more formal investigations that ultimately lead to the same outcome. But it also seems clear that complementarity will continue to be a complex and loosely defined principle of jurisdictional constraint. As observed by the OTP, the Iraq/UK situation gave rise to complex factual and legal assessments on complementarity (para. 492-505). For the Prosecutor, “the preliminary examination has shown that there is a reasonable basis to believe that various forms of abuse were committed by members of British forces against Iraqi civilians in detention” (par. 493), but in terms of complementarity, the “test” was not successfully passed.

Some may consider the finding of prima facie information to support allegations of serious crimes committed by UK personnel inconsistent with the Prosecutor’s statement and ultimate decision to forego any further investigation. Such a conclusion is invalid. To the contrary, this outcome was the result of a rigorous interpretation of the statutory law and of the principle of complementarity, in strict conformity with her mandate. Respect for the process established by the Rome Statute is as central to the legitimacy of the Court as is the imposition of accountability for violations of its enumerated crimes. Indeed, there are rarely more troubling indications of the illegitimacy of a criminal tribunal that the tribunals failure to respect the procedures established by its organic charter.


Giovanni Chiarini is an Italian Attorney at Law (Bar Council of Piacenza, Italy), admitted as Assistant to Counsel (Conseils Adjoints) at the International Criminal Court (The Hague) list. He is a PhD candidate specialized in International and Comparative Criminal Procedure at Insubria University (Como, Italy), and was a Chercheur Invité at the Laboratoire de Droit International et Européen (LADIE), Université Côte d’Azur (Nice, France). He interned as a Law Clerk at the Supreme Court of the Extraordinary Chambers in the Courts of Cambodia (ECCC – Khmer Rouge Tribunal), with the United Nations Assistance to the Khmer Rouge Trials (UNAKRT). 

The author sincerely thanks Prof. Geoffrey Corn (South Texas College of Law, Houston, U.S.A.) for his enlightening review.