BRUSSELS - Last week's announcement by Scottish First Minister Alex Salmond that he intends to hold a referendum on Scotland's independence in 2014 implies uncharted legal territory for the EU.
A newly independent Scotland would raise a number of thorny questions around its relations with the European Union - including whether it would have to fully renegotiate membership and whether it would be obliged to become a member of the euro.
For the EU itself, the issue would present a political and legal conundrum. Never in the history has a member state broken up and then had its successor part seek EU membership (Greenland, which used to be part of Denmark, left the then EEC in 1985). The EU treaties contain no answers.
Salmond's Scottish National Party has insisted that an independent Scotland will simply remain in the EU and that it will have a referendum on whether to join the euro. It sees its large off-shore oil and renewable energy resources as very big bargaining chips.
But many constitutional experts do not believe automatic membership is a given.
"The position is that if Scotland became independent, England, Wales and Northern Ireland would continue as the rest of the United Kingdom. It would be the continuing state. That is the position of international law in practise," Jo Murkens, a constitutional law expert at the London School of Economics, told this website.
"Scotland would be a new state and as a new state would have to apply for EU membership."
It would need the approval of all 27 member states to come on board, with countries such as Spain, home to independence-minded Catalonia, likely to be wary of the move, however.
"There are lots of countries with secessionist movements who are likely to keep a very close eye on this. The break-up of a fully functioning liberal state - you can see why that's a problem," noted Murkens.
The legalities are just one side of the story. Member states could do as Salmond wishes and take the political decision to simply grant Scotland semi-automatic membership (voting rights and MEP numbers would still have to be negotiated).
Again, this would depend on the good will of all those member states harbouring potential breakaway statelets. "I don't see the incentive to make it easy for Scotland," Murkens said.
Some academics argue this should be the route. A 2011 pamphlet on "internal enlargement" by the Centre Maurits Coppieters, linked to the regionalist faction in the European Parliament, says the EU would have to accept a Scottish state as not to do so would breach the Union's democratic principles.
It says it would require a handful of steps: a formal notification to the EU of secession; recognition of the new state by the EU and treaty amendment.
A change in Scotland's status would also alter London's relations with the European Union, with its EU financial contributions, voting weight and annual rebate all affected.
Giving an idea of the complexity, one EU source noted: "What are the consequences for EU funds, for example? They go to regions, but this is administered by a central authority for the UK. There would be a lot to talk about."
The currency question
With discussions only beginning to deal with the mechanics of a possible Scottish state, one of the major questions concerns the euro.
Scotland currently falls under the UK's general opt-out from the euro. But negotiating as a new member state would mean the opt-out no longer applied - unless member states agreed that Edinburgh could keep it.
Instead as a new member state, Scotland would be obliged to join the single currency, although it would retain the right to decide when.
A paper published last year by the House of Commons library suggested that an independent Scotland would have to pay almost €10 billion into the eurozone's permanent bailout fund (ESM).
The extent of Scottish people's affection for the EU is likely to be tested still further by the paper's other findings.
It noted that should Scotland become independent, the 5 million-strong state will have to contribute significantly more to the EU's coffers and may lose out on the share it gets of the British rebate - the yearly millions of euros London gets back from Brussels in return for its extensive agriculture payouts.
The European Commission, for its part, is firmly staying out of the politically awkward debate. "We don't comment on hypothetical questions," said spokesperson Mark Gray.
Will it happen?
And the question may remain hypothetical.
The referendum date was not chosen at random - Scotland will in 2014 host two big sporting events, the Commonwealth games and the Ryder Cup, creating a buzz. It will also mark the 700th anniversary of the Battle of Bannockburn, a historic Scottish victory over English soldiers.
But polls consistently show that a majority of Scots wants to remain part of the UK. A recent YouGov survey found 61 percent oppose independence, while 39 favour it.
In the event of a vote for independence, Scotland would have to sort out its bilateral relations with the rest of the UK.
"The division of Czechoslovakia in 1992 required 30 treaties and 12,000 legal agreements," Constitutional affairs expert Professor Robert Hazell, from University College London, recently wrote.
And even then all may not be clear. Hazell is of the opinion that the Scottish people would be legally entitled to two referendums - one on whether to enter independence negotiations with the UK and a second on whether they agree to the terms of the separation, including the terms of EU membership.