At para. 38 of the Impugned Decision, the Trial Chamber had found:

The target of such an Order [under Rule 54bis] is material that the organisation possesses. Questions of ownership and whether the material was initially obtained by another are irrelevant. As the Appeals Chamber explained in the Blaškić Subpoena Decision [Blaškić Judgement on Review Request], “the obligation under consideration [that of Article 29] concerns [inter alia] action that States may take only and exclusively through their organs (this, for instance, happens in case of an order enjoining a State to produce documents in the possession of one of its officials).” This applies equally to material received by one State from another. Of course, should a third-party holder of sensitive material assert that its legitimate security interests would be adversely affected by an order for production, it may seek appropriate protective measures.

The Appeals Chamber found that the Trial Chamber “erred […] when summarily dismissing the issues of ownership and origination of information as irrelevant to a Rule 54bis order.” (para. 43). It held:

43. […] Nothing in the text of Rule 54bis or the jurisprudence concerning the International Tribunal’s power to issue compelling orders to States[1] precludes consideration of these matters or indicates that the only question of concern for a Trial Chamber is whether or not the State is in possession of the requested information or documents. Furthermore, the Appeals Chamber recalls that the Rules of the International Tribunal have been intentionally drafted to take into account certain State interests and to provide safeguards for them in order to encourage States in the fulfilment of their obligation to cooperate with the International Tribunal under Article 29 of the Statute.[2] Indeed, under Rule 54bis, a Judge or a Trial Chamber is required to consider the national security interests raised by a State in determining whether to issue a Rule 54bis order or whether to direct, on national security interests grounds, protective measures for the documents or information to be produced by a State under a Rule 54bis order.[3]

It then held that “a properly tailored Rule 54bis order would necessarily avoid requiring production of information over which the United States does not have ownership” (para. 45).

See paras 44-45 for the complete reasoning.