Chapter 2
Jurisdiction of South African Courts and Institution od Prosecutions in South African Courts in Respect of Crimes (ss 4-5)
5 Institution of prosecutions in South African courts
(2) No prosecution may be instituted against a person accused of having committed a crime if the crime in question is alleged to have been committed before the commencement of the Statute.
Jurisdiction ratione temporis
Non-retroactivity
EDIT.