With power comes responsibility. In their new duties, Trump administration officials will need to consider the legal hazards associated with supporting foreign military partners who commit international crimes. Perhaps most alarming to some officials will be the risk of personal criminal liability. When might this arise? The White House recently said it is open to cooperating with Russia to combat ISIL, and Rex Tillerson, in his nomination hearings, said the Syrian Kurds “have been our greatest allies … that we intend to continue to support.” What could possibly go wrong? Think about support for the Syrian Kurds and U.S. forces transferring detainees to them, or U.S. arm sales to the Saudi-led coalition in Yemen, or sharing intelligence with Russia to conduct operations in Syria. In some cases, the analysis may turn on whether the support makes a “substantial contribution” to crimes committed by the foreign partner—a key element for complicity under customary international criminal law.

The concept of complicity appears in multiple incarnations in international law (see this mini-symposium for a survey). In international criminal law, complicity doctrines allocate individual criminal responsibility in the face of collective violence, which depends on a division of roles and tasks among multiple actors. A complicity theory may also ensure conviction in situations in which a prosecutor cannot prove that the defendant possessed the heightened mental element (mens rea) associated with the underlying crime (e.g., a so-called specific intent crime), but can prove that the defendant knowingly rendered assistance to another perpetrator who possessed the requisite mens rea. In public international law, the term “complicity” is employed to ascribe responsibility to states that act via proxies or surrogates in the territories of other states or otherwise contribute to breaches of international law at the hands of non-state actors. Likewise, it can be relevant when states work in coalition together and one state breaches international law. Complicity doctrines also have the potential to ensure some measure of accountability when the primary perpetrator is out of reach of the relevant tribunal for whatever reason. For example, principles of foreign sovereign immunity may bar suit against a repressive foreign government directly but not against a multinational company engaged in a joint venture with the state. Likewise, while the United States cannot be brought before European courts or the European Court of Human Rights, individuals who have been subjected to extraordinary rendition have successfully filed claims against European states that played a part in their capture, detention, or transfer.

The plain text of the statutes of the original ad hoc international criminal tribunals did not provide much detail as to the elements of complicity liability; as such, it was left to the parties and judges to add content to these concepts through the identification of applicable customary international law. To do so, they looked to relevant precedent from the World War II period, the drafting history of various multilateral treaties, and general principles of penal law as exemplified in the world’s legal systems. Through this deductive process, the ad hoc tribunals developed a rich jurisprudence around complicity liability.

Substantial Assistance/Contribution

Articulations of the doctrine of complicity in international criminal law have long included a requirement that the accomplice’s acts of assistance make something akin to a “substantial contribution” to the substantive crime committed.  Although the doctrine has been formulated in slightly different ways over the years by different tribunals, it is clear that this is a fact-based inquiry.  The crux of the inquiry requires an evidentiary interrogation as to whether the defendant’s conduct or omissions made the charged crime more likely and/or whether the crime would have occurred in the same way had the alleged aider/abettor not acted in the way s/he did. Showing that the defendant exerted an actual influence on a crime committed is necessary, though not to the point of proving “but for” causation. The case law reveals that even limited involvement can have the requisite “substantial effect” on the commission of a crime, because the focus is on the impact of the defendant’s actions vis-à-vis the criminal conduct charged.

This element of the complicity doctrine has a long pedigree, tracing back to World War II-era jurisprudence before U.S. military tribunals convened under Control Council Law No. 10 and other postwar fora.  This legal history is exhaustively traced by the International Criminal Tribunal for the Former Yugoslavia (ICTY) in its landmark Furundžija opinion.

Complicity in the Planning, Preparation or Execution of a Crime

The ICTY has adjudicated cases in which the accused aided and abetted at one or more of three possible stages of the crime or underlying offence—“planning, preparation or execution.” (Milutinović, ¶91). Thus, the ICTY made clear that the assistance provided need not be contemporaneous with the criminal act (Orić, ¶283). For example, it ruled in Delalić, a case involving detainee abuses:

Subject to the caveat that it be found to have contributed to, or have had an effect on, the commission of the crime, the relevant act of assistance may be removed both in time and place from the actual commission of the offence (¶352) (emphasis added).

There, the Appeals Chamber affirmed a defendant’s acquittal on the ground that even though he had contacts with the Red Cross and had been interviewed by journalists about Čelebići Camp, where civilians were unlawfully confined, it was open to the Trial Chamber to conclude that any effect of this conduct was insufficiently “significant” to hold the defendant responsible as an accomplice to the charged acts.

The physical or psychological assistance or support can be rendered to the perpetrator directly or by way of an intermediary (Orić, ¶282). Even limited involvement, or the carrying out of routine duties, can have a substantial effect on the realization of the crime; the precise degree of involvement is dealt with at sentencing (Popović, ¶1765; Blagojević & Jokić  ¶¶197-99). Unlike the doctrine of conspiracy, no evidence of a plan or agreement “between the aider and abettor and the physical perpetrator or intermediary perpetrator is required” to satisfy the requirements of complicity (Milutinović, ¶91).

An Omission Can Make a Substantial Contribution

Even omissions and inaction can constitute “substantial contributions.” The failure to act, however, is not enough to ascribe liability absent a legal duty to prevent the crime. That duty may be derived “from a bystander’s position or authority as a superior or actual leader” (Orić, ¶283). In these cases, complicity doctrines often intersect with the doctrine of command or superior responsibility.

In Mrkšić (¶553), for example, the accused was under a duty to prevent the commission of the underlying offence and failed to do so; the ICTY found him guilty because his inaction had a substantial effect upon the commission of the crime and he possessed the requisite knowing state of mind. In that case, the defendant had ordered the withdrawal of troops who had been guarding prisoners of war. Mrkšić’s subsequent failure to ensure the prisoners’ wellbeing was deemed to have rendered substantial practical assistance to Serb paramilitary forces—whom he knew to be out for revenge and who subsequently abused the Croat prisoners (¶¶621-27).  Mrkšić was also charged under a superior responsibility theory of liability, which was deemed superfluous in light of this finding of complicity (¶634). Mrkšić’s co-accused, by contrast, was found not guilty of the abuse when his only involvement was to be present while prisoners were being removed from a hospital earlier in the day, well before the abuse had begun (¶637).  Similar reasoning was employed with respect to Pandurević, who was found liable where he had a duty to protect the prisoners and the means to prevent his subordinates from participating in the charged crimes (Popović, ¶1792).

Likewise, Lazarević’s conviction was reversed upon a finding by the ICTY Appeals Chamber that “no reasonable trier of fact could have found beyond reasonable doubt that his omission … had a substantial effect on the commission of the forcible displacement, i.e. that it would have been substantially less likely [to have occurred] had Lazarević taken … further measures,” such as filing additional criminal reports or initiating additional investigative or disciplinary proceedings since the military justice system’s failures were beyond his control (¶¶1679-82). This latter ruling indicates that just having a role in an abusive system alone is not enough to trigger liability as an accomplice (Furundžija, ¶233).

The International Criminal Tribunal for Rwanda (ICTR) has also weighed in here with respect to culpable omissions, although most of the defendants before that Tribunal were prosecuted under a conspiracy theory of responsibility.  In Ntagerura, et al. (¶659), the ICTR stated that a culpable omission required the following elements:

  1. the accused must have had a duty to act mandated by a rule of criminal law;
  2. the accused must have had the ability to act;
  3. the accused failed to act intending the criminally sanctioned consequences or with awareness and consent that the consequences would occur; and
  4. the failure to act resulted in the commission of the crime.

In that case, it was relevant that Bagambiki had “a legal duty under Rwandan domestic law to ensure the protection of individuals within his prefecture” and that he was empowered to request the intervention of the security services to ensure public order (¶660). Bagambiki was ultimately acquitted on the grounds that although the Prosecutor had proven that Bagambiki had participated in identifying for questioning certain individuals accused of being affiliated with the rebel Tutsi-led Rwandan Patriotic Front (RPF), there was insufficient evidence that he had been involved in their subsequent death (¶674). He was also acquitted under a superior responsibility theory because no superior-subordinate relationship had been proven between hum and the direct perpetrators (¶677). Judge Williams penned a strong dissent, arguing that the Tribunal should have drawn the logical inference that Bagambiki must have either sent the perpetrators to kill the individuals whom he had selected or given his tacit approval for this outcome. Judge Williams reasoned, “Amidst the political climate at the time, with the pervasive killing of Tutsis in the prefecture, it stands to reason that such a denouncement by a public figure of such standing put the selected refugees at greater risk” (¶13).

The Provision of Means

In Aleksovski, the Tribunal explained that “substantial assistance” can “consist of providing the means to commit the crime or promising to perform certain acts once the crime has been committed, that is, behaviour which may in fact clearly constitute instigation or abetment of the perpetrators of the crime” (Aleksovski, ¶62; Krstić, ¶¶137-44). Thus, a commander can be liable if s/he provides logistical support to the commission of a crime or otherwise permits “the use of resources under his or her control, including personnel, to facilitate the perpetrator of a crime” (Popović, ¶1784).

Pandurević, for example, was the commander of the so-called Zvornik Brigade, which provided various forms of support (such as the transfer of prisoners) and materiel (including ammunition and machines to bury the victims) to other Serb soldiers who committed the massacre in question (Popović, ¶1785). Similarly, Blagojević was found guilty under a complicity theory for permitting the use of his brigade’s resources—including personnel who participated in separating the men from the women and in guarding and transporting victims—to facilitate the commission of the crimes (Blagojević & Jokić, ¶¶130-34)). The Appeals Chamber rejected the defendant’s argument that his troops were “inconsequential” in the “overall context of the event” (¶134). In the same case, defendant Jokić was convicted of aiding the Srebrenica killings by providing engineering machinery and personnel for burial operations after-the-fact (Blagojević & Jokić, ¶¶197-99). The Trial Chamber found that this aid was part of the larger plan and assisted the direct perpetrators of the crimes (Blagojević & Jokić, ¶¶201-204).

No Causation Required

There is no requirement of proving strict causation in the complicity jurisprudence. As stated by the ICTY, it “is unnecessary to prove that a cause-effect relationship existed between participation and the commission of the crime. The act of participation need merely have significantly facilitated the perpetration of the crime” (Aleksovski, ¶61).  Thus, there is no need to prove that “the crime or underlying offence would not have been perpetrated but for the accused’s contribution” (Milutinović, ¶92). It is enough that the accused’s conduct made “the performance of the crime possible or at least easier” (Orić, ¶282).

The Approving Spectator

In Furundžija, an accused was charged with complicity in rape and other sexual violence.  His involvement in the events in question encompassed being present in the room while a subordinate interrogated and then sexually assaulted the victim.  The Tribunal went so far as to rule (¶232) that even the provision of moral support, unaccompanied by tangible conduct, could constitute complicity in a crime so long as that support “directly and substantially” assisted in the commission of a crime. The ICTY has consistently accepted this sort of “approving spectator” cases (see, e.g., Aleksovski, ¶64).  That said, it must be shown that the accused had a status that meant his or her presence during the criminal activity could be construed as legitimizing or encouraging the relevant conduct, that the accused knew that his or her presence would have such an effect, and that the accused’s presence was in fact construed by the principal perpetrators as providing support for their actions (Simić, ¶130).

Thus, in Simić, the Appeals Chamber found that the defendant had aided and abetted the unlawful arrests and detention of the victims; however, he was acquitted of their subsequent mistreatment because the Appeals Chamber was not satisfied that the only reasonable inference that could be drawn was that the defendant lent substantial assistance to the beatings of detainees, because there was no evidence that he had visited the detention centers or that the principal perpetrators were under his authority (¶130). His decision to deny them health care did, by contrast, lend substantial assistance to their confinement under inhumane conditions (¶134).


Thanks to Marissa Brodney for her excellent research assistance for this post.

Image: Kurdish People’s Protection Unit, or YPG, at the outskirts of Kobane, Syria, June 20, 2015 –Ahmet Sik/Getty