LONDON – If Britain votes to leave the EU on Thursday, it'll be final. Irreversible. Irrevocable. No appeals. No second chances.
"Out is out," European Commission President Jean-Claude Juncker told reporters Wednesday.
"You can't jump out of the airplane and then clamber back into the cockpit," is how British Prime Minister David Cameron put it in a radio interview a few hours earlier.
But what if a vote to leave weren't really that final or dramatic? Some experts are wondering whether Britain can ever really free itself from the European Union — even if voters strongly endorse hitting the eject button. Others say it's not out of the question that Brits could find themselves going back to the ballot box in a few years' time if buyer's remorse sets in.
"The EU is a bit like the Hotel California in the Eagles song," said Tim Oliver, a fellow at the London School of Economics' IDEAS foreign policy think tank. "You can check out anytime but you never really leave."
Much of the uncertainty stems from the ambiguity about what a British exit, or Brexit, really means. Abandoning Europe could mean anything from a sweeping withdrawal from EU institutions to more limited opt-outs which could leave major pillars of European integration, such as free movement of labor, untouched.
"'Leave' could mean a million different things," Oliver said, giving Britain's political establishment considerable scope to loiter in Europe's lobby as euroskeptics argue over where the exits are.
Experts say there might be even more room for maneuver in the months and years following an "out" vote.
In theory, a two-year countdown goes into effect after a European country formally notifies its partners of its intention to quit the union, but complex international negotiations routinely run on for years and the parties involved could let the deadline lapse as talks drag on, perhaps even past Britain's 2020 parliamentary elections.
What if voters' minds change between now and then? And even if the negotiations over Britain's departure were concluded on time, what would happen if the U.K. were presented with unfavorable terms?
One expert said he could envisage a last-chance referendum asking Brits whether they still wanted to leave the EU under those conditions.
"It is at least legally possible and it might create the political space for a government to back out of an exit," said Gavin Barrett, an expert on European constitutional law at University College Dublin. "I think a case could be made for a second referendum asking, 'Do you really want this?'"
The let's-vote-on-this-one-more-time maneuver has helped bail out the European project before, albeit under different circumstances. After Irish voters rejected EU reforms in 2008, politicians in Dublin won modest concessions from their European counterparts and ran the vote again the following year, this time with a positive outcome. Similar EU referendum do-overs turned an Irish "No" into a "Yes" in 2002 and helped secured a Danish "Ja" in 1993.
But the path to a second referendum in Britain is far narrower, in part because — unlike in Ireland — the political establishment is split over Europe. If leading euroskeptic Boris Johnson takes the reins of the ruling Conservative Party following a vote to leave the EU, the prospect of a final vote will fade further still.
Alan Renwick, the deputy director of the Constitution Unit at University College London, said a do-over would only be plausible "if a party wins the 2020 election on a platform of having a second referendum and trying to go back in."
That seems unlikely given the current political alignment, but he said nothing is completely out of the question when it comes to a potential Brexit.
"You have so many possible long shot scenarios," he said. "If you add up the probabilities of all of them, you end up with a significant chance of something surprising happening, whatever that might be."