As a principle of criminal law it is recognized for example in the European Convention on Human Rights[3] as well as the United States Constitution.
Legal systems vary considerably in the extent to which they apply the principle to civil and administrative laws.
The United States Supreme Court has for example often denied retroactive effect to its constitutional rulings on criminal procedure.
[7] Historically, the principle of non-retroactivity of statutory law emerged in the ancient Roman Republic, becoming fully established by the second century BCE.
This represented an evolution from earlier conception of the legal principles (ius) as unchanging and statutes as merely clarifying this existing law.