In the Name of the Cambodian People and the United Nations and Pursuant to the Law on the Establishment of the Extraordinary Chambers in the Courts of Cambodia for the Prosecution of Crimes Committed During the Period of Democratic Kampuchea

Nuon Chea, Ieng Sary, Ieng Thirith, Khieu Samphan, and Kaing Guek Eav (defendants) were under investigation by the Extraordinary Chambers in the Courts of Cambodia (ECCC) for violating Geneva Conventions and committing crimes against humanity pursuant to Art. 5, 6, and 29 of the Law of Establishment under the ECCC. Sary filed a motion to the judges (OCIJ) investigating the matter, arguing that (1) joint-criminal-enterprise (JCE) liability was recognized as customary international law neither currently nor during the time of the alleged crimes (1975–1979) and (2) no legal authority under the Law of Establishment, Cambodia law, or international agreements existed to apply JCE liability by the ECCC. Sary claimed that category III of JCE (JCE III) was supported only by customary international law where there was widespread acceptance of its application. Sary also argued that absent opinio juris, the enforcement of JCE III was unlawful. The OCIJ denied the motion in part, holding that the actus reus and mens rea of JCE categories I and II and the actus reus of JCE III were enforceable by the ECCC because they preexisted the investigation. However, the OCIJ granted the motion as to the mens rea of JCE III (results of a common plan being foreseeable) because it was not established under international law at the time of the investigation and was thus inapplicable by the ECCC. Sary appealed.