than a requirement of statute law. One exception is Article 29, section 4, subsection 9° of the Irish constitution: The State shall not adopt a decision taken by the European Council to establish a common defence pursuant to Article 42 of the Treaty on European Union where that common defence would include the State. This was originally inserted by the 2002 amendment ratifying the Treaty of Nice, and updated by the 2009 amendment ratifying the Treaty of Lisbon. An earlier bill intended to ratify the Treaty of Nice did not include a common defence opt-out, and was rejected in the first Nice referendum, in 2001. The Defence Act 1954, the principal statute governing the Irish Defence Forces, did not oblige members of the Irish Army to serve outside the state (members of the Air Corps and Naval Service were not so limited). A 1960 amendment was intended to allow deployment in United Nations peacekeeping missions, and requires three forms of authorisation, which since the 1990s have come to be called the "triple lock": A UN Security Council resolution or UN General Assembly resolution; A formal decision by the Irish government; Approval by a resolution of Dáil Éireann (the lower house of the Oireachtas or parliament, to which the government is responsible). These provisions were modified in 1993 to allow for Chapter VII missions and again in 2006 to allow for regionally organised UN missions. History Before independence Before the creation of the Irish Free State, the whole island of Ireland was part of the United Kingdom of Great Britain and Ireland from 1801 to 1922; the pre-1801 Kingdom of Ireland was under siege of Britain (and before 1707 the Kingdom of England). While Irish unionists supported political integration with Britain, Irish nationalists were divided between those who envisaged some continuing link with Britain and the "advanced nationalists", mainly republicans, who wanted total independence. Separatists generally envisaged an independent Ireland being neutral, but were prepared to ally with Britain's enemies in order to secure that independence, reflected in the maxim "England's difficulty is Ireland's opportunity". Irish leaders in the Nine Years' War (1594–1603) allied with Spain. Wolfe Tone's 1790 pamphlet Spanish War claimed that Ireland was not obliged to support Britain if the Nootka Crisis started a war with Spain; Tone later sought France's aid for the United Irishmen Rebellion of 1798. At the outbreak of the First World War, James