Barroso's first Commission term expired on 31 October 2009. Under the Treaty of Nice, the first Commission to be appointed after the number of member states reached 27 would have to be reduced to "less than the number of Member States". The exact number of Commissioners was to be decided by a unanimous vote of the European Council, and membership would rotate equally between member states. Following the accession of Romania and Bulgaria in January 2007, this clause took effect for the next Commission. The Treaty of Lisbon, which came into force on 1 December 2009, mandated a reduction of the number of commissioners to two-thirds of member-states from 2014 unless the Council decided otherwise. Membership would rotate equally and no member state would have more than one Commissioner. However, the treaty was rejected by voters in Ireland in 2008 with one main concern being the loss of their Commissioner. Hence a guarantee given for a rerun of the vote was that the council would use its power to amend the number of Commissioners upwards. However, according to the treaties it still has to be fewer than the total number of members, thus it was proposed that the member state that does not get a Commissioner would get the post of High Representative – the so-called 26+1 formula. This guarantee (which may find its way into the next treaty amendment, probably in an accession treaty) contributed to the Irish approving the treaty in a second referendum in 2009.