302.    […] Article 6 (3) of the Statute establishes a duty to prevent a crime that a subordinate was about to commit or to punish such a crime after it is committed, by taking “necessary and reasonable measures”. The Appeals Chamber recalls that the interpretation of “necessary and reasonable measures” has been considered in previous cases before ICTY. The Čelebići Trial Judgement found that:

[A] superior should be held responsible for failing to take such measures that are within his material possibility… [T]he lack of formal legal competence to take the necessary measures to prevent or repress the crime in question does not necessarily preclude the criminal responsibility of the superior”.[1]

          The Appeals Chamber agrees with this interpretation and further notes that the Trial Chamber applied a similar approach when it found that:

In order to establish responsibility of a superior under Article 6 (3), it must also be shown that the accused was in a position to prevent or, alternatively, punish the subordinate perpetrators of those crimes. Clearly, the Trial Chamber cannot demand the impossible. Thus, any imposition of responsibility must be based upon a material ability of the accused to prevent or punish the crimes in question.[2]

          Thus, it is the effective capacity of the Accused to take measures which is relevant.  Accordingly, in the assessment of whether a superior failed to act, it is necessary to look beyond formal competence to actual capacity to take measures. […]