OFFENCES OUTSIDE CANADA
7.
Application before coming into force
*(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.
*[Note: Section 7 in force October 23, 2000, see SI/2000-95.]
Non-retroactivity
Nullum crimen sine lege
Customary international law
EDIT.