The huge expansion and establishing the fundamental divide of power in EU
In 2003 the Nice treaty entered into force. For the most part it is a technical update of the system without too many fundamental changes. Most changes were made to the processes used for getting legislation through the system in another effort to make the upcoming expansion easier. In particular larger countries lost the second commissioner and procedures involving vetoes were put aside. Another inclusion was a fundamental rights charter with basic human rights.
Only a single country voted on the treaty: Ireland. At first the result was a 53 % rejection. Reasons varied from fear of weakening of western economies, weakened influence for smaller countries, loss of agricultural support and the formulation of a right to abortion which doesn't sit well with the more devout Catholics. Since the participation was a measly 34 % of the voters, the Irish government somehow got the exact same treaty up for another vote a year later where it passed with 63 % voting yes and an improvement in participation to almost 50 %.
The large and long anticipated expansion of EU finally happened 2004 where 10 new countries joined at the same day. Czech Republic, Cyprus, Estonia, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia were welcomed into EU through votes leading up to may 1 2004. It is by far the biggest expansion of EU ever! Most countries had solid majorities for joining the union although Maltas vote was somewhat close at 53,7 % voting yes.
Later in 2004 the EU constitution was signed. The constitution is meant as exactly that: A paper delineating the fundamental rights in the union.
Since the constitution is imposing a flag, a national anthem, a motto, the euro as the official currency and celebration of a Europe day in memory of Robert Schumans visions in 1950, it is safe to say that it is very ambitious and probably close to Schumans vision of a European federation. Furthermore, it is giving EU wide competences and includes “...the progressive framing of a common defense policy that might lead to a common defense”, which is a bit more cautious than the Maastricht treaty. The problem with the constitution was the need for national referendums in all european countries. The first vote in Spain was a clear yes, but already in europephile France and Netherlands the constitution was voted down. In France it was presumably mostly a national dissatisfaction with Jacques Chirac as well as fear of a far too liberal market. In Netherlands, speculations ran on people finding EU too arrogant and elitist as well as the constitution being “anti-socialistic”. This referendum was the first given to the people of Netherlands since their politicians were among the founding members of the ECSC.
The council did not have a plan b. After the two neigh-votes on the constitution the council called for a “pause for reflection”. The result was to make a new treaty to act as a “soft” constitution.
In 2009 the final result of the negotiations, the Lisbon treaty, came into force. The only place holding a referendum was Ireland where the treaty fell in 2008 with 53 % voting no in a vote with above 50 % participation. After the vote, the council gave the Irish a legally binding guarantee that Irish sovereignty on matters such as taxation, military neutrality and family matters like abortion would not be harmed. 16 months later the exact same treaty, though this time with some binding guarantees, was approved by a large majority of 67 %!
Sources
http://www.theguardian.com/world/2002/oct/18/eu.politics1
http://europa.eu/legislation_summaries/institutional_affairs/treaties/nice_treaty/nice_treaty_introduction_en.htm
http://news.bbc.co.uk/2/hi/europe/3954327.stm
http://news.bbc.co.uk/2/hi/8288181.stm