Related Rule
Australia
Practice Relating to Rule 101. The Principle of Legality
In the Polyukhovich case before Australia’s High Court in 1991, in which the accused was charged with crimes committed during the Second World War, Judge Brennan considered the matter of retrospective criminal laws in international law:
[I]international law not only refuses to countenance retrospective provisions in international criminal law; it condemns as offensive to human rights retrospective municipal criminal law imposing a punishment for [a] crime unless the crime was a crime under international law at the time when the relevant act was done. 
Australia, High Court, Polyukhovich case, Legal Reasoning of Judge Brennan, 14 August 1991, § 37.