Ultra Vires


Bystanders to Evil: Toward a Principled Approach to Omission Liability Under the Doctrine of Joint Criminal Enterprise


Kerry Sun (2L) and Karlson Leung (2L)

Karlson and Kerry at the Peace Palace in The Hague.

The International Criminal Tribunal for the former Yugoslavia (ICTY) was established by the UN Security Council following the outbreak of conflicts in the territory of the former Yugoslavia during the early 1990s. This was the most tumultuous and violent period in Europe since the Second World War and saw the birth of several new states, namely Serbia, Croatia, Bosnia and Herzegovina, Montenegro, Macedonia, Slovenia, and Kosovo. The Tribunal sought to bring to justice those most responsible for serious international crimes perpetrated in the region, and was the first international tribunal established since the Nuremberg Trials. The ICTY is situated in The Hague and is anticipated to close after completing all remaining court proceedings by November 2017.

Joint criminal enterprise (JCE) is a key legal doctrine that has developed through the jurisprudence of the ICTY. JCE, first set out in the 1999 Tadić Appeal Judgement, is both a form of “commission” of a crime under Article 7(1) of the ICTY Statute and a mode of liability for crimes committed by a group of persons. Under the doctrine of JCE, an accused may be held criminally responsible for the crimes committed by other JCE members, where there is a plurality of persons; a common criminal purpose carried out jointly or by some members of this plurality of persons; and the participation of the accused in the common criminal purpose through a “significant contribution”. Three categories of JCE exist, with differing actus reus and mens rea elements.

In the context of the Tribunal, this doctrine allowed for the prosecution of individuals who may not have physically participated in the crimes, but were nonetheless part of a group that was responsible for crimes against humanity, war crimes, or genocide in the territory of the former Yugoslavia.

This past summer, Kerry Sun and Karlson Leung interned at the ICTY, with the support of the International Human Rights Fellowship Program. Kerry Sun was a Legal Intern with the Office of the Prosecutor (Trial Division) at the ICTY. He assisted the Prosecution trial team in the Mladić case. Karlson Leung was a Legal Intern working for Judge Carmel Agius in the President’s Office, Chambers. He assisted with two appeals, Stanišić & Župljanin and Prlić et al..

The views expressed do not reflect the views of the Office of the Prosecutor, the President’s Office and the Chambers, or other organs of the International Criminal Tribunal for the former Yugoslavia, or the United Nations. Errors and omissions are solely the fault of the respective author.


Kerry Sun (2L)

Former Legal Intern, Office of the Prosecutor (Trial Division)


In the recent case of Prosecutor v Stanišić & Župljanin, the ICTY Appeals Chamber considered the nature of omissions that give rise to criminal responsibility under the doctrine of joint criminal enterprise (JCE). The accused, Mićo Stanišić and Stojan Župljanin, were high-ranking officials within organs of the Republika Srpska in 1992 during the Bosnian War. In 2013, the Trial Chamber found them liable for crimes against humanity and war crimes as part of a JCE to permanently remove non-Serbs from the territory of a planned Serb state. Each accused was found to have participated in this JCE, partly on the basis that he had failed to take steps to prevent certain crimes against the non-Serb population.

To be found liable under the JCE doctrine, the accused must have “significantly contributed” to the JCE by performing an act or omission that was directed to the furtherance of the common criminal purpose of the JCE. However, prior to Stanišić & Župljanin, it was unclear whether “significant contribution” by omission required the accused to have violated a pre-existing legal duty, and if so, what the requisite nature of the legal duty was.

Liability for omissions is well-established under the ICTY Statute. Article 7(1) of the Statute imposes criminal responsibility on a person “who planned, instigated, ordered, committed or otherwise aided and abetted” a crime. Although it does not explicitly refer to omissions, the Tribunal has held that Article 7(1) encompasses liability for “commission by omission” as well as “aiding and abetting by omission”. Additionally, command responsibility under Article 7(3) incorporates a requirement of failing to act. According to ICTY jurisprudence, “commission by omission” liability requires that the accused violate a legal duty to act mandated by a rule of criminal law, while possessing the capacity to act. Likewise, “aiding and abetting by omission” requires the combination of a legal duty under international humanitarian law and the accused’s capacity to act.

In Stanišić & Župljanin, the accused argued that similar requirements applied to “significant contribution” by omission to a JCE. Since the doctrine of JCE is considered a form of “commission” under Article 7(1) of the Statute, it was submitted that the relevant legal standard for “commission by omission” should apply to “significant contribution” by omission—that is, that the accused must have violated a legal duty mandated by a rule of criminal law while having the capacity to act.

On June 30, 2016, the Appeals Chamber released its judgment. Rejecting the accused’s submissions, the Chamber decided that “significant contribution” did not require the violation of any legal duty, whether criminal or non-criminal. It held that a legal duty and the accused’s capacity to act are not necessary to, nor determinative of, JCE liability. Instead, any act or omission can constitute a “significant contribution” to a JCE, which is “a question of fact to be determined on a case-by-case basis.” The Appeals Chamber thus affirmed the Trial Chamber’s finding that the accused significantly contributed to the alleged JCE, and upheld the convictions.

Although the Appeals Chamber directly resolved the issue, its treatment of omission liability under JCE was unsatisfactory for several reasons. Significantly, the Judgement did not specify the threshold at which an omission would constitute a “significant” contribution. Since value judgments are inherent in the criminalization of omissions, it is imperative that omission liability is carefully defined so as to preserve legal certainty and predictability. The Appeals Chamber provided little guidance on the meaning of “significant contribution,” creating uncertainty about when inaction would become criminal. Nor is guidance available from elsewhere in the jurisprudence. The meaning of “contribution” thresholds in the ICTY and ICTR case law remains an open question; for example, under aiding and abetting liability, the element of “substantial contribution” has generally been defined negatively or merely described as requiring “a fact-based inquiry.”

Furthermore, the approach to JCE omissions in Stanišić & Župljanin was inconsistent with the Tribunal’s jurisprudence. Despite the fact that the ICTY conceptualizes JCE as a form of “commission” under Article 7(1), the Appeals Chamber departed from the requirements for “commission by omission” of a legal duty and capacity to act. The Chamber held that under Article 7(1), commission by omission and JCE are distinct modes of liability, with different legal elements. Yet this is an unconvincing justification for dispensing with the requirement of a legal duty under JCE. Rather, the relevant parallel is that under both commission by omission and JCE liability, acts and omissions are treated as normatively equivalent: the accused is punished for the ultimate crimes to which he contributed, whether by act or omission, and not for having made the contribution itself. By suggesting that any failure to act can constitute participation in a JCE, even without a duty to act, the Appeals Chamber arguably overextended criminal liability for omissions.

Related to the equivalence of acts and omissions are the difficulties associated with evaluating the legal and moral significance of inaction. As commentators have observed, inaction differs from action in two important ways. Generally, the impact of inactions is not as apparent as those of actions. In addition, a person’s state of mind is not as readily inferred from inactions, compared to actions; a person may fail to act for a multiplicity of reasons. Such considerations, and concerns about interference with individual autonomy, favour a more restricted approach to omission liability.

It might be objected that a capacious view of significant contribution, an actus reus element of JCE liability, is justified by the mens rea requirement that an individual must possess an underlying intent to pursue a common criminal purpose with other JCE members. However, this approach is unsound in the context of omissions. Consider the mens rea of aiding and abetting by omission, which requires knowledge that the accused’s conduct assists in the commission of a crime. In contrast, under JCE liability, an accused does not need to perform an act or omission with the knowledge that his conduct constitutes a contribution to the JCE. In theory, this seems to suggest that an individual could be found to have “significantly contributed” to a JCE, and potentially liable for all the crimes of JCE members, by doing nothing and without knowing that his inaction amounted to a contribution. While highly unlikely to occur in practice, this nevertheless sits uncomfortably with the principle that all JCE participants are held equally culpable.

What could the Appeals Chamber have done instead? A principled approach would have at least explicitly recognized an accused’s “capacity to act” as a necessary element of a “significant contribution” by omission to a JCE. The Chamber could have adopted the requirement of a pre-existing legal duty, even while accepting that such a duty could arise from a non-criminal or domestic law. Because of the Trial Chamber’s undisturbed findings that both Stanišić and Župljanin were in fact under domestic legal duties to protect the non-Serb population, the outcome of the appeal would likely not have changed. Indeed, requiring the violation of a legal duty could usefully reflect the requisite threshold for “significant” contribution, thus enhancing legal certainty. Alternatively, it could have decided that where omissions are concerned, a significant contribution to a JCE requires the accused’s knowledge that his omission constitutes such a contribution. The adoption of such changes would place an under-theorized area of the ICTY’s jurisprudence on a more principled basis.


Karlson Leung (2L)

Former Legal Intern, Chambers (President’s Office)


When an individual refuses to offer life-saving assistance to his or her detainees or stands by silently while his or her soldiers commit serious war crimes – when any intervention would have prevented the atrocity – one cannot help but ask if such conduct should be treated as equivalent to actively contributing to the deaths of the victims. In other words, can conduct that is essentially passive amount to the same heinousness as an active act or decision? Amongst the ICTY’s achievements, one of the main legal precedents was the clarification of the notion of “superior responsibility,” and the idea that military commanders must prevent and punish serious crimes for which subordinates are responsible. Over the span of the last two decades, the Tribunal has expanded the jurisprudence in international criminal law and on the issue of omission liability more broadly.

Omission liability

In the recent rendering of the appeal judgement for the case of Stanišić & Župljanin, the Appeals Chamber clarified the legal standard on omission liability as it relates to what constitutes a significant contribution to the Joint Criminal Enterprise. The JCE doctrine was developed by the ICTY in its early cases and refers to the common criminal purpose behind the perpetration of serious crimes and persecution on the basis of the victims’ group identity. A salient question is whether it is morally justified to punish an inaction to the same degree as an action. As international criminal law scholar Michael Duttwiler explains, “a crime of omission, in a sense, criminalizes the neglect of a positive duty to act,” and can be defined in two forms. The first is one where there is an inherent duty built in and failure to act is criminalized, while the second is defined as a normatively equivalent action and punishable due to the moral blameworthiness of failing to prevent the reprehensible results. The second form of omission looks at commission through omission, which is grounded on a legal duty to prevent harm from occurring, and not just upon moral expectations. ICTY jurisprudence is ripe with examples where omissions have led to convictions: in Mucić the Tribunal dealt with the failure to provide detainees with adequate amenities in prison, in Blaškić the use of human shields was considered an omission in that the perpetrators failed to move the civilians away from the targets, and in Krnojelac the authorities’ failure to address deteriorating prison conditions amounted to inhuman and cruel treatment. By criminalizing failures to act, international criminal law has made important steps towards ending impunity for commanders who have shirked responsibility for those acting under their de facto supervision.

Stanišić & Župljanin

The issue of omission liability came to the forefront of Mićo Stanišić and Stojan Župljanin’s appeal, a case involving two officials and the events that occurred in Bosnia and Herzegovina following the creation of the Republika Srpska during the Yugoslav conflicts. Stanišić was the Minister of the Interior, and Župljanin was the Chief of the Regional Security Service Centre of Banja Luka and a member of the Crisis Staff of the Autonomous Region of Krajina.

Župljanin’s ground of appeal alleged that omission liability was over-criminalized because it relied on domestic criminal duties. However, the Appeals Chamber dismissed the appeal, and reasoned that a duty to act that meets the legal conditions for commission by omission is not required when dealing with participation in the JCE. This line of reasoning may have been advanced to address a concern raised by some academics, namely that reliance on domestic criminal law would defeat the very purpose of international criminal liability, given that national legislatures would determine liability. Some academics of international law, such as Lars Berster of the University of Cologne, have proposed that a principle of control – which is already reflected in forms captured by ICTY case law (see, for example, Brđanin, Čelebići, and Limaj et al.) – should be used as the basis for deriving duties to act from international criminal law.

In response to concerns that the “significant contribution” threshold is unclear and the issue raised by my colleague about what exact threshold is required for the actus reus of JCE liability, a contextual case-by-case approach is appropriate. Contributions need not even be criminal in and of themselves, so long as the accused performs acts, or fails to perform acts, in the furtherance of the JCE. This approach allows for a greater range of acts to be caught in the net of liability, given that acts of persecution can take many forms and a variety of people – from bureaucrats and administrators to military personnel – are responsible in such an enterprise.

My colleague also raised allegations of inconsistency with requirements for commission by omission and aiding and abetting by omission: namely that the law demands more from the aider and abettor (as an accessory to the crime) than a principal to JCE (which only requires a “significant contribution”). However, these concerns are overblown. Aiding and abetting by omission requires four threshold conditions, as set out in Ntagerura et al., relating to knowledge of the crime and capacity to act. However, the stringent mens rea for participating in the JCE requires a “sharing of intent” to participate in the crime, and conviction requires that both the actus reus and mens rea requirements are satisfied. In the Appeal Judgement, the Appeals Chamber was correct in employing a “lower threshold” for the actus reus component of JCE liability, given that a case-by-case examination of the acts that lead to furtherance of the JCE allows for a more nuanced take of each individual’s level of responsibility.

Despite some ambiguities and potential areas for future development, international criminal law has made significant strides since the Second World War on omission liability, which is a major constituent part of cases involving serious international crimes. Over the years, the ICTY has sent a clear signal that when those that have power over perpetrators could have intervened to stop or prevent abuses but chose not to do so, they open themselves to criminal liability and the call for them to face justice for their actions – or non-action.  

In front of the Stari Most (Old Bridge) in Mostar, Bosnia and Herzegovina.
In front of the Stari Most (Old Bridge) in Mostar, Bosnia and Herzegovina.


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