The referendum on Scottish independence has deep implications not only for the future of the British union, but also for the union of 28 countries that has shaped European politics for more than 50 years.
Scotland's membership of the European Union has emerged as a key issue in the independence debate. In Brussels, officials have closed ranks on the issue. Despite repeated questioning from journalists last week, the European Commission refused to say what a Yes vote would mean for Scotland's EU membership, insisting it did not want to interfere in an internal matter.
This was evidently not the view of European Commission president José Manuel Barroso in February when he told BBC's Andrew Marr Show it would be "extremely difficult, if not impossible" for Scotland to join the EU, noting that the new state would have to reapply and secure the agreement of all other member states.
The issue is a highly political one. Barroso himself cited Spain's refusal to recognise Kosovo, a former province of Serbia, as an example of the resistance felt by some countries towards recognising breakaway states for fear of setting a precedent.
Venice in Italy and Flanders in Belgium are two regions where secessionist feeling is strong, but arguably Belgium has succeeded in containing Flemish nationalism by developing a sophisticated decentralised and federalist system of government that gives more power to the regions.
Belgian model
That Belgium, despite its strong internal divisions, has successfully avoided slipping into violence as a way of dealing with its social and political divides, is testimony to its successful model of federalism.
Catalonia is a different matter. The issue is a highly sensitive one for Madrid. Unlike Britain, Spain has refused to recognise a referendum scheduled in the prosperous northern region later this year, a decision that British prime minister David Cameron may now be quietly envying.
Spanish prime minister Mariano Rajoy intervened yesterday, on the eve of the referendum, asserting it would take Scotland eight years to renegotiate membership of the European Union.
In reality, the exact legal position of Scotland’s relationship to the European Union, should it choose independence, is unclear.
The core issue is whether Scotland, as a new state, would have to apply for EU membership like any other would-be member as set out in Article 49 of the EU treaty, a view that is held by the British government and Spain. In contrast, Scotland argues that membership could be worked out via Article 48, which allows member states to make amendments. Alex Salmond argues that this could be achieved by March 2016, the projected date for Scottish independence.
Absurd
Pro-unionists point out that Article 48 would require unanimous agreement from all member states, including countries such as Spain and
Greece
, which is concerned about the implications for
Cyprus
. But equally, the suggestion that Scotland, which has been a member of the European Union for 41 years via its membership of the
United Kingdom
, be treated the same as other pre-accession states like
Moldova
, and even
Ukraine
, appears absurd.
As former European Parliament president Pat Cox argued earlier this month in an article in the Scotsman, the EU has previously accommodated change that was "democratically mandated but not foreseen by the treaties". The relatively seamless incorporation of East Germany into the Union for example shows that, when it comes to the complexity of European Union politics, where there's a political will, there's a way.
Nonetheless, the idea that Scotland would automatically accede is equally unfeasible. The new state would be unlikely to keep some of the specific concessions previously accorded to Britain such as the British rebate negotiated by Margaret Thatcher. The question of whether Scotland, along with Britain and Ireland, can remain outside the Schengen free travel area is also a matter of contention, as EU rules oblige all new member states to sign up to Schengen.
Similarly, the EU's accession criteria include an obligation for acceding states to join the euro currency, though Britain and Denmark previously negotiated an opt-out clause that allows them to remain outside the euro area.
Key battleground
With Scotland’s future currency one of the key battlegrounds in the independence debate, there is a critical question of whether Scotland would retain access to the British opt-out on euro membership should it manage to retain sterling as the national currency.
What is certain, however, among the mountain of information surrounding the Scottish referendum, is that a Yes vote for Scottish independence would immediately spark an unprecedented flurry of EU legal wrangling.
With a possible British referendum on EU membership looming on the horizon, the implications for EU law are profound.