terror statutes which do not cover crimes committed in IS held territory. Though the UNSC has the power
to establish an ad hoc tribunal that could adjudicate these crimes,4 as it did in the situations of Rwanda and
the former Yugoslavia, the likelihood of that happening in the context of IS appears limited. Under these
circumstances, it remains to be seen whether the International Criminal Court (ICC or Court) —set up to end
impunity for the perpetrators of the most serious crimes of concern to the international community— should
play a role. While a tempting solution, there are a number of potential obstacles to the Court’s involvement.
This article sets out the primary impediments to adjudicating crimes of IS and suggests ways in which these
difficulties might be overcome. At the outset, the article will analyse why the ICC should seek to assert
jurisdiction over IS, rather than leave prosecution to domestic forums. It then deals with the three primary
spheres in which challenges present themselves: (1) jurisdictional —given the limitations contained in the
Rome Statute in terms of what events can be prosecuted; (2) subject matter —focusing specifically on acts
of terrorism in light of the absence of a specific criminalisation thereof in the Statute; and (3) the means of
holding certain types of participants in IS crimes to account —looking at the regime of liability contained in
the Rome Statute.
II. Why the ICC Should Seek to Assert Jurisdiction over IS
The ICC operates on the basis of complementarity, with the primary responsibility for exercising criminal
jurisdiction over those responsible for international crimes resting on States Parties.5 The ICC will only step
in where there are no national proceedings occurring in States with jurisdiction,6 or where such States are
unable or unwilling genuinely to investigate or prosecute.7
With the obvious absence of prosecutions in Syria, Iraq and Libya, some domestic prosecutions of IS
members and sympathisers have taken place in the jurisdiction of ICC States Parties.8 These cases invariably
involve nationals posing a domestic threat as a result of either being involved in recruitment or supporting
activities for IS within the State, or returning to the State after fighting for IS.9 Identification and detention
of returning fighters also presents a challenge.10 Where prosecuted, offences in the domestic sphere there-
fore tend to be breaches of domestic anti-terror laws as opposed to offences committed in IS held territory.11
Consequently there is a near complete accountability gap for IS members active in Syria, Iraq, and Libya. A
core difficulty for domestic authorities who might otherwise assert jurisdiction is that of apprehending such
individuals in areas under IS control. Even if suspects were to be detained, extradition for the purposes of
domestic prosecution may be hampered, given the limitations of the existing legal framework combating
terrorism through extraditions.12 Other issues likely to arise include the differences between legal systems
with regard to classification of offences and punishments.13 This includes possible questions of prosecuto-
rial integrity and the upholding of due process rights, where, for example, there is public anger regarding
a suspect or where the suspect is deemed to be an intelligence asset.14 States may also decide for security
4 Christopher Greenwood, ‘International Law and the “War Against Terrorism”’ (2002) 78 International Affairs 301, 305.
5 Rome Statute of the International Criminal Court (adopted 17 July 1998, entered into force 1 July 2002) 2187 UNTS 90 (Rome
Statute) prmbl, art 1.
6 The Prosecutor v Germain Katanga and Mathieu Ngudjolo Chui (Judgment on the Appeal of Mr Germain Katanga Against the Oral
Decision of Trial Chamber II of 12 June 2009 on the Admissibility of the Case) ICC-01/04-01/07-1497 (25 September 2009) para 78.
7 The Prosecutor v William Samoei Ruto, Henry Kiprono Kosgey and Joshua Arap Sang (Judgment on the Appeal of the Republic of
Kenya Against the Decision of Pre-Trial Chamber II of 30 May 2011 entitled ‘Decision on the Application by the Government of
Kenya Challenging the Admissibility of the Case Pursuant to Article 19(2)(b) of the Statute’) ICC-01/09-01/11-307 (30 August
2011) para 41.
8 See eg Karen J Greenberg and others, ‘Case by Case: ISIS Prosecutions in the United States’ (2016) Center on National Security at
Fordham Law Report.
9 Tina Bellon, ‘Germany Arrests Suspected ISIS Fighter Returning from Syria’ (Business Insider, 18 March 2016)
nessinsider.com/isis-fighter-germany-arrested-suspect-2016-3> accessed 27 February 2017; The Crown Prosecution Service, ‘Anjem
Choudary and Mohammed Rahman Charged for Inviting Support of ISIL’ (5 August 2015) .uk/news/lat-
est_news/anjem_choudary_and_mohammed_rahman_charged_for_inviting_support_of_isil/index.html> accessed 27 February
10 HL Deb 28 April 2016, WA8065.
11 See eg US Department of Justice, ‘Virginia Teen Pleads Guilty to Providing Material Support to ISIL’ (Press Release, 11 June 2015)
accessed 27 February 2017.
12 See eg Pouyan A Mazandaran, ‘An International Legal Response to an International Problem: Prosecuting International Terrorists’
(2006) 6 International Criminal Law Review 503, 522.
13 ibid 525.
14 ibid 524–525.