ex post facto law (Latin for "from after the action" or "after the facts") is a law that retroactively changes the legal consequences (or status) of actions that were committed, or relationships that existed, before the enactment of the law

Article 11, paragraph 2 of the Universal Declaration of Human Rights provides that no person be held guilty of any criminal law that did not exist at the time of offence nor suffer any penalty heavier than what existed at the time of offence. It does however permit application of either domestic or international law.