Crimes Against Humanity and War Crimes Act 2000
7 (5) Where an act or omission constituting an offence under this section occurred before the coming into force of this section, subparagraphs (1)(a)(ii) and (2)(a)(ii) apply to the extent that, at the time and in the place of the act or omission, the act or omission constituted a contravention of customary international law or conventional international law or was criminal according to the general principles of law recognized by the community of nations, whether or not it constituted a contravention of the law in force at the time and in the place of its commission.
Jurisdiction
Entry into force
Jurisdiction ratione temporis
Non-retroactivity
Nullum crimen sine lege
Customary international law
EDIT.