The International Criminal Court is reliant on the cooperation of states and their enforcement authorities since it does not have a police force of its own. Hence, cooperation is of paramount importance to the operation of the Court at all stages of its work. However, this chapter notes that the Appeals Chamber has had limited cause to examine this issue, having only considered a handful of appeals concerning the attendance or questioning of witnesses and the freezing of assets. One theme that runs through these decisions is that the Appeals Chamber has supported readings of the Rome Statute which provide the Court with the powers it needs to conduct proceedings as effectively as possible, without imposing obligations on States that go beyond those expressly set out in the Rome Statute. This chapter observes that the Chamber has discretion as to whether it will refer a case of non-cooperation with such discretion being contingent on whether engaging external actors in that manner will be the most effective way of obtaining cooperation. Such a referral is simply a means of obtaining cooperation, not a punishment for failure to cooperate.