7 Principle of Ex Post Facto Law (Non-Retroactivity)

The rule: no retroactive criminal law — conduct judged by the law in force at the time of the act. An ex post facto law (making past conduct criminal, or aggravating past conduct's punishment) is prohibited: Constitution, Article 20(4) (again); ICCPR Article 15; the classic American constitutional prohibition (the US Constitution's ex post facto clauses).The two permitted exceptions (examiners test them):1. Lex mitior (the milder law): if subsequent law reduces punishment (or decriminalizes), the offender gets the benefit — retroactivity in favour of the accused is not only allowed but required by ICCPR Article 15's second paragraph;2. International crimes' special case: the Nuremberg-era problem — punishing acts that were criminal under international law though possibly not under domestic statute at the time — the ICCPR permits trial for acts that were criminal according to the general principles of lawrecognized by the community of nations (the jus cogens/international-crimes exception).The syllabus prescribes a case for this section; its citation and holding are withheld until verified.