Non-retroactivity

Legal principle

Non-retroactivity is the legal principle that laws do not apply retroactively and ex post facto laws are forbidden. This principle may be applied to judicial decisions as well as statutory law. The principle of non-retroactivity is widely recognized for international laws such as treaties, although treaties can have retroactive effect if the parties so intend. It is also widely recognized in criminal law, at least to the extent of prohibiting criminal sanctions that were not in place at the time of the crime. As a principle of criminal law it is recognized for example in the European Convention on Human Rights as well as the United States Constitution.

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