Ratification is the act of giving official sanction or approval to a formal ocument such as a treaty or constitution. It includes the process of adopting an international treaty by the legislature, a constitution, or another nationally binding document (such as an amendment to a constitution) by the agreement of multiple sub-national entities. The process of ratifying a constitution is most commonly observed in federations such as the United States, confederations or international organisations sui generis such as the European Union.