Ex post facto law
A law that changes legal consequences retroactively.
An ex post facto law is a law that retrospectively changes the legal consequences or status of actions that were committed, or relationships that existed, before the enactment of the law. In criminal law, it may criminalize actions that were legal when committed; it may aggravate a crime by bringing it into a more severe category; it may change the punishment prescribed for a crime; it may extend the statute of limitations; or it may alter the rules of evidence to make conviction likelier. Conversely, a form of ex post facto law called an amnesty law may decriminalize certain acts, or simply prohibit prosecution, or enact that there is to be no punishment while leaving the conviction technically unaltered. A pardon has a similar effect but applies to a single case rather than a class of cases. Other legal changes may alleviate punishments retroactively, known by the Latin term in mitius.
- field
- Law
- known_for
- Retrospective alteration of legal consequences
- related_concepts
- Amnesty law, pardon, in mitius, lex mitior
- prohibited_in
- United States (constitutional), Canada (Charter, with exceptions), European Convention on Human Rights, ICCPR, American Convention on Human Rights
- permitted_in
- Some parliamentary supremacy nations, Australia (limited), Brazil (only if beneficial), Croatia (exceptionally justified), Denmark (historical use), Finland (exceptional instances)
Lore & Background
Ex post facto laws have been used historically in various countries. Australia passed retrospective laws in the early 1980s to prosecute tax avoidance, and legislation criminalizing certain war crimes retrospectively has been held constitutional.
Reader's Guide
Ex post facto laws raise fundamental questions about fairness, legal certainty, and the rule of law. Many jurisdictions prohibit them in criminal matters, as seen in the U.S. Constitution, the European Convention on Human Rights, and the International Covenant on Civil and Political Rights. However, some nations allow them under specific conditions, such as when they benefit the accused (lex mitior) or for exceptionally justified reasons. The tension between parliamentary supremacy and individual rights is evident: countries like Australia have no strong constitutional prohibition, while Canada's Charter allows override via the notwithstanding clause. The concept remains controversial, as it can be used both to punish past wrongs (e.g., war crimes) and to violate principles of non-retroactivity. The existence of amnesty laws and pardons shows that retroactive legal change can also serve restorative or merciful purposes.
Did You Know?
- Ex post facto laws may extend the statute of limitations or alter rules of evidence to make conviction likelier.
- A pardon has a similar effect to an amnesty law but applies to just one case instead of a class of cases.
- Article 29 of the Constitution of Albania explicitly allows retroactive effect for laws that alleviate possible punishments.
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