Crimes Against Humanity and War Crimes Act 2000

6 (5) For greater certainty, the offence of crime against humanity was part of customary international law or was criminal according to the general principles of law recognized by the community of nations before the coming into force of either of the following:

(a) the Agreement for the prosecution and punishment of the major war criminals of the European Axis, signed at London on August 8, 1945; and

(b) the Proclamation by the Supreme Commander for the Allied Powers, dated January 19, 1946.

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.

Article 11
Jurisdiction ratione temporis
1. The Court has jurisdiction only with respect to crimes committed after the entry into force of this Statute.
2. If a State becomes a Party to this Statute after its entry into force, the Court may exercise its jurisdiction only with respect to crimes committed after the entry into force of this Statute for that State, unless that State has made a declaration under article 12, paragraph 3.