International treaties such as the European Union's Treaty of Rome or the Hague-Visby Rules have effect in English law only when adopted and ratified by Act of Parliament. Adopted treaties may be subsequently denounced by executive action, unless the denouncement or withdraw would affect rights enacted by Parliament. In this case, executive action cannot be used owing to the doctrine of parliamentary sovereignty. This principle was established in the case of "R (Miller) v Secretary of State for Exiting the European Union" in 2017.