Prohibition on Ex Post Facto Law

This option report compares constitutional provisions related to the prohibition on punishment by laws ex post facto. The sample of constitutions reviewed consists of almost 600 constitutions enacted since 1789. The report encompasses three different types of prohibitions, including those where: parliament shall have no power to declare acts to be infringements of the law which were not so at the date of their commission, penal laws shall not be retroactive against the accused, and no punishment may be laid down except by law and that it may be applied solely to acts previously deemed by law to be so punishable. In addition to detailing the trends with respect to such provisions, the report sets out sample constitutional provisions.