Having Regard to the Jurisprudence of the ICC, Consider Whether the Concept of ”Complementarity” in the Rome Statute is Working

Summary: 1. Introduction – 2. Principle of Complementarity in the Light of Doctrine Theories – 2.1 Complementarity as part of the Admissibility Test: Interpreting Article 17 Rome Statute – 2.2 Complementarity: One-Fold Test v. Two-Folds Test – 3. Interpretation and Application of the Concept of Complementarity in ICC Case Law – 3.1 One-Fold Test v.Two-Folds Test of the Concept of Complementarity in ICC Jurisprudence – 3.2 The “same person/same conduct” test – 3.3 Unwillingness and Inability to Carry out the Proceedings – 3.4 Unwillingness Genuinely to Carry out the Proceedings – 3.5 Inability Genuinely to Carry out the Proceedings – 4. Conclusions


The International Criminal Court (the ICC or the Court) is a permanent court, established by an international treaty, the Rome Statute of the ICC (Rome Statute), with the function to prosecute perpetrators of the most serious international crimes. It is an international insti-tution complementary to national criminal jurisdiction.[1]  This means that, unlike the ad hoc International criminal tribunals, the ICC does not have neither primacy over national courts nor the exclusive jurisdiction over international crimes.[2]

One of the most important principles, governing the functioning of the ICC regime, is the principle of complementarity. It reflects the balance between preserving state sovereignty, on the one hand, and fighting impunity for international crimes, on the other hand.

The former has been achieved by acknowledging that the primary responsibility in re-pressing serious crimes of international concern falls on national criminal tribunals[3]; the latter has been accomplished by empowering the Court to act in situations when there is no ”prospects of national trials”.[4]

The establishment of the complementary principle has a double effect: first, it provides an incentive for states to fight impunity on domestic level by investing and prosecuting international crimes[5]; second, it acts as a ”safety net” mechanism[6] in case of failure of States to prosecute international crimes.[7]

In this essay, it is firstly analysed the issue of the complementarity principle and its func-tioning under article 17 of Rome Statute. It examines the development of the one/two – steps complementarity test in the light of the doctrine theories. Second, it is investigated, having re-gard to the jurisprudence of the ICC, whether the concept of ”complementarity” in the Rome Statute is working, that is, if there is or not, effectively, a primacy of national jurisdiction over ICC one. In the case the answer is negative, it will be questioned what could be the possible solutions to make the complementarity more effective.

2. Principle of Complementarity in the Light of Doctrine Theories

2.1 Complementarity as part of the Admissibility Test: Interpreting Article 17 Rome Statute

The article 17 of the Rome Statute stipulates that the complementarity is concerning to the admissibility of a case rather than to the jurisdiction of the Court. Precisely the Court cannot exercise the jurisdiction that it has if a case is inadmissible.[8] Hence, the principle of complementarity does not influence the existence of jurisdiction of the Court as such, but it rules when this jurisdiction may be exercised by the Court.[9]

Consequently, article 17 works as a wall to the exercise of jurisdiction.[10]

Basically, the complementarity is, together with the gravity element, one of the two key points of the so-called ”admissibility test”.[11] It embraces, under article 17[12], three situations in which a case is inadmissible before the ICC:

  1. It is being investigated or prosecuted by a State which has jurisdiction over it, unless the State is unwilling or unable genuinely to carry out the investigation or prosecution;
  2. It has been investigated by a State with jurisdiction over it which has decided not to prosecute the persons concerned, unless the ”decision resulted from the unwillingness or inability of the State genuinely to prosecute”;
  3. The person concerned has already been tried for the conduct in question and a trial by the Court is not allowed under the Statute’s ne bis in idem rules.

If any of the three situations relating to complementarity is satisfied, the case will be in-admissible before the ICC; by contrary, if none of the conditions of inadmissibility is realized, the case will be admissible.[13]

2.2 Complementarity: One-Fold Test v. Two-Folds Test

The determination of inadmissibility on the grounds of complementarity has been the object of a long debate between the supporters of the so – called single–fold test, on one hand, and those in favour of the two-fold test, on the other hand.[14]

The former theory states that a case should be admissible before the Court only when the state, having the jurisdiction over alleged crimes, is unwilling or unable genuinely to carry out the proceedings. This approach to complementarity assumes ”unwillingness and inabil-ity” as the focal requirements of admissibility.

As a consequence, in the case of State inaction (absence of the national proceedings), the ICC shall evaluate the existence of un/willingness and/or in/ability of states and so the case cannot be found admissible before the Court merely on the ground of state inactivity[15]

The latter theory affirms that complementarity itself contains a test consisting of two “folds” or steps (the so – called two-fold tests) and precisely, the ICC shall evaluate if:

  1. there is an ongoing investigation or prosecution in a State, or an investigation or prosecution existed in the past (the so – called “proceedings requirement);
  2. only when the response to this evaluation is affirmative, it shall evaluate if the State is/was un/willing and un/able to carry out genuinely the proceedings.

The supporters of this theory consider that un/willingness and in/ability represent the “exceptions” to the real condition, that is, the existence of national proceedings.[16]

3. Interpretation and Application of the Concept of Comple-mentarity in ICC Case Law

3.1 One-Fold Test v.Two-Folds Test of the Concept of Complementarity in ICC Jurisprudence

The single–fold test was argued by Katanga’s defense in support of the appeal against the decision of the Trial Chamber on the admissibility in the Katanga – Chui case.[17]

The Appeals Chamber (AC) rejected the argument in favor of the single – fold test and it has confirmed the two-fold test. Essentially, the Court has held:

  1. firstly, in case of inaction, the question of unwillingness or inability does not arise;[18]
  2. secondly, unwillingness or inability genuinely to carry out proceedings, contained in subparagraphs (a) and (b) of article 17, cannot be the preliminary points to decide if the case is inadmissible because the complementarity regards, primarily, the presence or the absence of national proceedings.[19]

This interpretation has also been confirmed in Ruto and Muthaura cases[20] and also in Gaddaffi case[21], where the Court has held that it is necessary firstly to establish the existence of proceedings and, only in affirmative case, it may proceed to the second part of the test.

3.2 The “same person/same conduct” test

According to the prevailing ICC case law, a case can be found admissible before the ICC every time there is a lack of national proceedings and without the need neither to evaluate the willingness or ability of the State nor to examine the grounds behind the States’ choice not to prosecute. Instead, with the existence of the national proceedings requirement, it will be necessary to evaluate, also, the un/willing and in/ability of the State concerned.

The lack, inside the Rome Statute, to establish which elements the national proceedings must own to satisfy the ”proceedings requirement” under article 17, has been covered by means of the ICC’s case law, introducing the so – called ”same person/same conduct test”, whereby the proceedings requirement is satisfied when national proceedings cover the same individual and the same conduct alleged in the proceedings before the ICC.

This test has been originally developed by the Pre–Trial Chamber (PTC) in its decision on the admissibility of the case before the ICC in the Lubanga case.[22]

Precisely, Mr. Lubanga, charged for enlisting children crime before the ICC, challenged the admissibility of the case, on the basis of article 17, given that the national court of Demo-cratic Republic of Congo (DRC) had already investigated and charged the indicted of geno-cide and war crimes. In this occasion, the PTC has held that it is a condicio sine qua non, for the inadmissibility of a case before the ICC, that the national proceedings must encompass both the person and the conduct which are the subjects of the case before the Court.[23]

While the “same person” concept did not need any further clarification, the analysis fo-cused on the interpretation of “same conduct”, in relation to which the PTC has assumed a severe ”construction”, equating the conduct with ”same crime”.[24]

The restrictive inter-pretation of the “same conduct” as “the same crime” could lead on some problems in the application of the principle of complementarity, given that, in a situation of mass atrocities, it is unrealistic to expect that national proceedings could cover all the specific crimes. Also, it could be burdensome for states, challenging the admissibility, upon which it exists the burden of proof the same conduct.

A more flexible approach to the test was taken by the AC in two Kenyan cases[25], in which the AC has confirmed the need to apply the “same person/same conduct test”, but with the explicit specification that a case is inadmissible when the national proceedings cover the same individual and “substantially the same conduct” as alleged in the proceedings before the Court.[26] In those cases, however, the Court did not explain what it should exactly mean the adverb ”substantially”.

This gap was filled by the PTC, in Gaddaffi case[27] whose arguments have been confirmed by the AC.[28]

The Court has held that “substantially same conduct” happens when there is a ”large overlap” between the incidents under the lens of the Prosecutor and the national authorities, but it could hold even when ”the overlap is smaller”, for example, if the episodes surveyed by the state are more serious than the ones which are investigated by the Prosecutor.[29]

Thus, there would be “substantially same conduct” only when the differences between the facts and circumstances under national and international investigations are minimal and they are linked together in time, space and by their subject–matter.

Furthermore, the PTC has held that, in relation to same conduct, the assessment of do-mestic proceedings should focus on the alleged conduct and not on its legal characterization.[30]

In Al–Senussi case[31] the PTC has held the case inadmissible. A decision confirmed by the AC’s judgment.[32]

The PTC has held that the relevant factual aspects of Mr. Al – Senussi’s conduct, as alleged in the proceedings before the Court, to evaluate his criminal responsibility, had been investi-gated by the Libyan authorities, confirming that ”the same conduct” alleged against Mr. Al – Senussi in the proceedings before the Court was subject to Libya’s domestic proceedings.[33]

However, the same person and the same conduct test has been criticized by Judge Usacka, since the test should be accompanied by other specific criteria in relation to case by case conditions.[34]

Furthermore, under the dissenting opinion of the Judge Song, the request to the states to cover exactly the same conducts, considered by the Prosecutor, would mean to impose on the States an excessive burden of proof.[35]

3.3 Unwillingness and Inability to Carry out the Proceedings

As said above, unwillingness and inability will only be considered if the proceedings requirement has met. Also, if the same person and the same conduct test is successful, then, the Court shall evaluate the un/willing and in/ability of the state, with jurisdiction, to carry out genuinely proceedings.

3.4 Unwillingness Genuinely to Carry out the Proceedings

In order to determine the unwillingness to carry out a proceeding, in a particular case, the Court shall consider, having regard to the principles of due process, recognized by interna-tional law, three situations delineated into paragraph (2) of the article 17 of Rome Statute, that is:

  1. the purpose of shielding the person from criminal responsibility,
  2. unjustified delays inconsistent with the aim to bring the person to justice and,
  3. the dependence or partiality of the proceedings incompatible to bring the person to justice.[36]

In relation to this, the “due process thesis” considers that where a trial breaches due pro-cess rights of the accused, a state is “unwilling” to genuinely carry out the investigation or prosecution. Consequently, in this situation, the Court should step in.[37]

This theory, for some scholars, is not convincing because the normal situations referred by article 17 (2) would not jeopardize the accused, but, on the contrary, would be to his or her benefit. The Court should find a state ”unwilling” only if its legal proceedings are designed to make the defendant more difficult to be convicted.[38]

This approach has been confirmed in Al – Senussi case where the AC has held that the fact that a State does not respect the fair trial rights of the suspect does not mean that it is “un-willing genuinely to carry out the proceeding”; unwillingness must be primarily concerned with a suspect evading justice.

3.5. Inability Genuinely to Carry out the Proceedings

In order to determine inability, in a particular case, the Court shall identify three scenarios:

  1. a state is unable to obtain the accused;
  2. a state is unable to obtain the necessary evidence and testimony for putting the persons allegedly responsible on trial;
  3. the state is otherwiseunable to carry out its proceedings.[39]

In all three situations, the lack has to be due to the total or substantial collapse or unavail-ability of the judicial system, thus requiring proof of a causal link in each case.

For example, in Bemba case, the Court proceeded to verify the ability of the national au-thorities to pursue the proceedings and it has held the inability of them because, among other things, the budget of the Ministry of Justice was described as “ridiculously insignificant”.[40] In Gaddaffi case, the PTC has held the unavailability of the national judicial system of Libya. Precisely, it was unable to secure the transfer of Mr. Gaddaffi’s custody from his place of detention under the Zintan militia into State authority and there was not concrete evidence that this problem could be resolved in the near future.[41]

Also the Court has held the lack of capacity to obtain the necessary testimony due to the inability of judicial and governmental authorities to ascertain control and provide adequate witness protection.[42]

4. Conclusions

Looking at the jurisprudence of the ICC, in relation to the functioning of complementarity principle, it does not seem that there is a primacy of the national jurisdictions over the Court and so, it becomes difficult to consider the ICC as a Court of last resort.

It seems clear that the functioning of the complementarity principle, under article 17 and in the light of the Court’s judgments, is not flexible but it entails a detailed and deep exam, primarily with the same person/same conduct test and, in the affirmative case, with the un/willing and in/ability one.

Even if, in the last decisions of the ICC, the concept of same conduct seems it has been interpreted with less vigour than in Lubanga case, it still appears very hard for the States, challenging the admissibility, to provide evidence that the conduct investigated or prosecuted under national proceedings could cover the same conduct investigated or prosecuted before the Court.

Moreover, when states do not fail the same conduct test, this would be not sufficient to retain the state jurisdiction on the case yet, because the states are, also, under the scrutiny of the willing and ability test. Hence, it does not seem a street with many loopholes.

Perhaps, in relation to guarantee the state sovereignty, through the primacy of national jurisdiction, the complementarity principle seems more a result of a formal and political compromise. Regarding the will to put an end to impunity, it does not seem that the com-plementarity, as it has been conceived, encourages the states to investigate and prosecute international crimes.

Moreover, there are some doubts about the credibility of this principle given that the Court evaluates the admissibility of a case without any reference to objective parameters, but under its discretion.

Thus, to make the complementarity principle working better, it would be desirable an implementation of the positive complementarity concept, a theory elaborated by the office of the Prosecutor (OTP) and based on the partnership, between states and the Court, which aims at encouraging states to effectively investigate and prosecute international crimes on national level by facilitating proceedings and providing assistance to the national authorities.[43]

Furthermore, it would be desirable a more flexible and so more realistic application of the complementarity principle, endorsing the evaluation of the presence of connections or linking elements rather than rigid application of the same person/same conduct test.

For example, in the case of co-perpetration or contributing liability situation, in which there could be several crimes, committed in different space and time, by numerous perpetra-tors, but all related to the same criminal plane, the correlated proceedings could be directly carried on by the national courts, even if the same person/same conduct test would not be stricto sensu respected.


By Teresa Augusto, No part of this paper may be copied, reproduced or transmitted without prior permission of the author.

[1] Rome Statute of the International Criminal Court, 1998, art. 1 and par. 10 of the preamble

[2] M. Benzing, ”The Complementarity Regime of the International Criminal Court: International Criminal Justice between State Sovereignty and the Fight against Impunity”, Max Planck Yearbook/United Nations Law, Volume 7, 2003, pp. 591-632

[3] Rome Statute, preamble, par. 4

[4] B. Perrin, ”Making Sense of Complementarity: the Relationship between the International Criminal Court and National Jurisdiction, Sri Lanka J. Int’l L. 303, 2006, 18 (2)

[5] Rome Statute, preamble, par. 6

[6] see Perrin, supra, n.4, p. 301

[7] C. Stahn, ”Complementarity: a Tale of two Notion”, 2008, 19, Criminal Law Forum, p. 96

[8] J.T.Holmes, ”Complementarity: National Courts versus the ICC”, in A. Cassese/P.Gaeta/J.R.W.D. Jones, The Rome Statute of the International Criminal Court: A Commentary, 2002, Vol. 1, p. 667 et seq.

[9] J. Crawford, ”The drafting of the Rome Statute”, in P. Sands, From Nuremberg to the Hague: The Future of International Criminal Justice, 2003, p. 109 et seq.

[10] See Holmes, supra, n.8, p.672

[11] D. Robinson, ”The Mysteriousness of Complementarity”, in Criminal Law Forum, Vol. 21, N. 1, 2010, p.4

[12] Rome Statute, art. 17 (1) (a) (b)(c)

[13] See Robinson, supra, n.11, p.5

[14] ibid., pp. 15

[15] ibid., p.20

[16] ibid., p. 20

[17] Prosecutor v. Germain Katanga and Mathieu Ngudjolo Chui, ICC – 01/04-01/07-1497, 25 September 2009

[18] ibid., par.78

[19] ibid., par. 74-79

[20] Prosecutor v. Ruto et all, ICC – 01/09 -01/11 – 101, 30 May 2011, par. 48 – Prosecutor v Muthaura et all, ICC – 01/ 09 – 02 / 11 – 96, 30 May 2011, par. 44

[21] Prosecutor v. Saif Al-Islam Gaddaffi, ICC – 01/11 – 01/11 – 344- Red, 31 May 2013, par. 89

[22] Prosecutor v. Thomas Lubanga Dyilo, ICC – 01/04-01/06, 09 March 2006, par. 31

[23] ibid., par. 31

[24] L. M. Keller, ”The Practice of the international Criminal Court: Comments on the Complementarity Conundrum”, 2010, 8 par.1, Santa Clara Journal of International Law 209

[25] See Ruto and Muthaura, supra, n. 20

[26] ibid., Muthaura, par. 39

[27] See Gaddafi,supra, n. 21

[28] Prosecutor v Gaddaffi and Al – Senussi, Judgement on the appeal of Libya against the decision of the Pre – Trial Chamber of 31 May 2013, Appeal Chamber, ICC – 01/11 – 01/11, 21 May 2014, par. 71 – 76

[29] ibid., par. 72

[30] See Gaddafi,supra, n.21, par.88

[31] Pre -Trial Chamber I, The Prosecutor v. Saif Al-Islam Gaddafi and Abdullah Al-Senussi, Decision on the admissibility of the case against Abdullah Al-Senussi, 11 October 2013, ICC-01/11-01/11

[32] The Appeals Chamber,Prosecutor v Saif Al-Islam Gaddafi and Abdullah Al-Senussi, N. ICC-01/11-01/11 OA6, 24 July 2014

[33] See Al-Senussi, supra, n. 31, par.164

[34] Separate Opinion, par.58

[35] Separate Opinion, par. 6

[36] Rome Statute, article 17, par. 2

[37] K.J. Heller, ”The Shadow Side of Complementarity: The Effect of Article 17 of the Rome Statute on National Due Process”, in Criminal Law Forum, Vol. 17, 2006, p.2

[38] E.C. Rojo, ”The Role of Fair Trail Considerations in the Complementarity Regime of the ICC: From ”No Peace without Justice” to ”No Peace with Victor’s Justice”?, Leiden Journal of International Law, vol. 18, (4), 2005, pp. 835-837

[39] Rome Statute,article 17 (3)

[40] Prosecutor v Bemba Gombo, ICC T. Ch. III, 24 June 2010, paras 21 and 245

[41] See Gaddafi, supra, n.21, par. 215

[42] See Gaddafi, supra, n.21, par. 209

[43] OTP, Informal Expert Paper, ”The Principle of Complementarity in Practice”, available at www.icc-cpi.int, last access 29 February 2016


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