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; it may extend the statute of limitations; or it may alter the rules of evidence to make conviction likelier. Conversely, an amnesty law may decriminalize certain acts, or a pardon may have a similar effect in a single case. Other legal changes may alleviate punishments retroactively, known by the Latin term in mitius.
- field
- Criminal and constitutional law
- known_for
- Retrospective alteration of legal consequences
- key_principle
- Prohibition or allowance of retroactive criminal laws
- related_concept
- Lex mitior (the milder law)
- international_treaties
- European Convention on Human Rights, International Covenant on Civil and Political Rights, American Convention on Human Rights
Lore & Background
Some common-law jurisdictions do not permit retroactive criminal legislation, though new precedent generally applies to events before the judicial decision. Some countries, such as the United States, explicitly forbid ex post facto laws in their constitution. In nations with parliamentary supremacy, ex post facto laws may be possible. In a nation with an entrenched bill of rights or written constitution, ex post facto legislation may be prohibited or allowed; for example, Article 29 of the Constitution of Albania explicitly allows retroactive effect for laws that alleviate possible punishments.
Reader's Guide
Ex post facto laws raise fundamental questions about fairness, legal certainty, and the rule of law. Their prohibition in many jurisdictions reflects a principle that individuals should not be punished under laws that did not exist at the time of their actions. However, exceptions exist, such as amnesty laws or retroactive mitigation of punishment (in mitius). The tension between parliamentary sovereignty and constitutional rights is evident in countries like Canada, where the Charter prohibits ex post facto criminal laws but allows override via the notwithstanding clause. International human rights instruments generally prohibit retroactive criminalization, though European jurisdictions often apply the milder law principle, allowing retroactive application if it benefits the accused. The debate continues over whether civil retroactive laws, such as those affecting property or taxation, should be treated differently from criminal ones.
Did You Know?
- Ex post facto laws may criminalize actions that were legal when committed.
- A form of ex post facto law called an amnesty law may decriminalize certain acts.
- Article 7 of the European Convention on Human Rights prohibits ex post facto criminalization.
- Some European countries apply the principle of lex mitior, which applies the milder law retroactively.
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