David Cameron had previously ruled out holding a second referendum, calling it "a once-in-a-lifetime event". However, Jolyon Maugham QC, a barrister specialising in tax law, argued that a second referendum on EU membership could be triggered by one of two scenarios: following a snap general election won by one or more parties standing on a remain platform, or as a result of parliament deciding that circumstances had changed significantly enough to require a fresh mandate. Maugham cited several instances in which a country's electorate have been asked to reconsider the outcome of a referendum relating to the EU, among them the two Treaty of Lisbon referendums held in Ireland, in 2008 and 2009.