The Treaty of Nice, which paves the way for the enlargement of the European Union, has finally come into force. The details of the treaty were agreed by EU leaders at a marathon summit in Nice in December 2000, but it then had to be ratified by every EU member state. Ireland submitted its ratification documents in December, the last country to do so. That set 1 February 2003 as the date when the treaty becomes law. The Treaty of Nice is long, complex and often confusing. But without it, the European Union would not be able to add 10 new members to its ranks on 1 May next year. What Nice does is to set out the institutional arrangements which will govern the new, enlarged EU. It increases the size and some of the powers of both the European Commission and the European Parliament. The commission will have 25 members - up from 20. The five biggest countries will no longer have two commissioners each.