Australia's High Court today disqualified Deputy Prime Minister Barnaby Joyce to sit in parliament as he held dual citizenship, when elected. Joyce was disqualified over a 116-year-old constitutional ban on dual citizens sitting in Parliament. <br/><br/>The ruling could cost the government its slender majority in Parliament as Prime Minister Malcolm Turnbull's conservative coalition has a single-seat majority in the 150-seat House of Representatives. Joyce will be able to stand for re-election, having renounced the New Zealand citizenship he unknowingly inherited from his father. <br/><br/>With the government trailing the opposition Labour Party in opinion polls, voters could use the by-election to toss both Joyce and his government out of office.