EU's Lisbon Treaty comes into force

Since that time, the European Union has grown by 12 member states to encompass almost 500 million citizens, expanded the area where the euro is employed as the currency to 16 countries, and sees its main challenges as tackling climate change, dealing with the effects of globalisation, and lately trying to exit the economic crisis.

The path to today's ratification however has been far from smooth, leaving the European Union with barely a month since 2001 when the institutional question was not an issue up for debate.

The body of the treaty was drawn up via a one-year convention, hailed at the time for containing a broad mix of representatives including national and European politicians and civil society representatives and headed by former French president Valery Giscard d'Estaing.

But the European Constitution that emerged was in 2005 torpedoed by voters in founding member states France and the Netherlands, shocking the EU and sending everyone back to the negotiating table.

Bumpy path

The resulting Lisbon Treaty contains most of the constitution's innovations but no longer the symbolically important and state-like elements such as an article covering an EU flag and anthem. It was also presented differently as simply an amending treaty, rather than a constitution in its own right.

This is largely a reflection of the nature of the European Union, made up of 27 member states, which to a greater or lesser degree want to further integrate in certain - but not all - areas.

Controversy and delays have continued to dog the treaty even in its new form. It too was rejected, this time by Irish voters in June 2008 who then changed their minds to embrace it a second referendum in the October of the following year. Meanwhile the Czech Republic's ratification, the final of the 27, was a drawn-out process involving multiple court assessments before the eventual reluctant signature by its eurosceptic president.

This meant that news that the treaty could finally to pass into force was marked rather by a sense of weary relief in member states than any sort of celebration.

New posts and new powers for MEPs

Its most prominent innovations include the creation of a permanent president of the European Council and a beefed up foreign policy chief, who will head a new large diplomatic corps.

These posts are supposed to give coherence to the bloc's external policy and supply it with a stronger voice on the world stage, although their success – ultimately awarded to a pair of low-profile politicians - will depend on the ability of member states to form united positions and support the new external policy chiefs.

The arguably more profound change is internally, with member states' ability to veto being markedly reduced and a corresponding significant boost to the European Parliament's powers. MEPs now have a say over a wide range of new areas including farm and fisheries policy, transport, structural funds and justice and home affairs.

Tax, social security issue, citizens' rights, the main aspects of foreign and defence policy and where EU institutions sit geographically are still subject to agreement by member-state unanimity, however.

National parliaments also gain some powers to scrutinise legislation to make sure it is proportionate and being enacted at the right level, while the signature of one million citizens across the EU obliges the commission to look into acting on the issue concerned.

The European Court of Justice gains the powers to rule in the area of freedom, security and justice as well as judging whether member states are implementing EU laws according to the Charter of Fundamental Rights – a rights document that all member states except Britain, Poland and the Czech Republic have signed up to.

The treaty, so long in the making, has both ardent proponents and vehement critics. Its admirers say it will make internal EU decision-making easier, more flexible and more democratic while its innovations will allow the EU to become a major player in the globe.

Its critics, however, say the central issue of the EU's democratic deficit has not been sufficiently addressed, meaning citizens will continue to perceive the European Union as being an elites-driven project.