Ratification is the process of adopting an international treaty, or a constitution or other nationally binding document (such as an amendment to a constitution) by the agreement of multiple subnational entities. The process of ratifying a constitution is most commonly observed in federations such as the United States or confederations such as the European Union.
Different organizations have different rules for how a constitutional change is ratified. Federations usually require the support of both the federal government and a certain percentage of the subsidiary entities. Some ratification processes also require a supermajority within legislatures.
The ratification of international treaties follows the same rules as the passing of laws in most democracies. An important exception is the United States, where treaty ratification requires a two-thirds majority in the U.S. Senate (and the United States House of Representatives does not vote on it at all). This makes it considerably more difficult in the US than in other democracies to rally enough political support for international treaties.
Ratification of the United States Constitution
See History of the United States Constitution.
Ratification of the European Constitution
The process for ratifying the "European Constitution"—a proposed constitutional document for the European Union (EU)—will vary from country to country; at least nine member states plan to hold referendums. The first state to ratify the constitution, Lithuania, did so on 11 November 2004. To take effect, the constitution must be ratified by all the member states of the EU. For more, see Treaty establishing a constitution for Europe.
The ratification of the current Constitution of Ireland was achieved by plebiscite in 1937.