If Britain votes to leave the EU, a divorce would have to be negotiated. It could lead to an orderly transition or a much more unpredictable process, buffeted by political pressure, volatile markets and the clash of national interests.

Leaving the EU is a daunting challenge with no clear precedent. Brexit would unwind economic relations of “incomparable complexity and depth”, according to Stephen Weatherill, professor of law at Oxford university. He argues it would be more legally complicated than decolonisation or the break-up of sovereign countries in the past.

The negotiation would not just concern divorce, the technical parting of ways and the settling of old bills. It would also have to re-engineer the world’s biggest single market, setting new terms of access and legislating to “renationalise” volumes of law rooted in the EU.
.
House of Commons research has estimated that EU-related law makes up at least a sixth of the UK statute book. That excludes 12,295 EU regulations with direct effect on everything from bank and consumer rules to food standards, which cease to apply the moment Britain leaves.  Britain would also have to renegotiate or reconfirm a web of EU-negotiated free trade deals with dozens of countries that anchor the UK in world commerce but are not automatically inherited if it leaves.

To prevent the bloc from unravelling, EU countries may seek to punish Britain, so others dare not follow its exit path. “They would try to make it as painful as possible, be it financially painful or politically painful,” said Gordon Bajnai, a former Hungarian prime minister. “The UK would face a hostile Europe.”

 

 

Pro-leave politicians liken such predictions of doom to past warnings over Britain’s rejection of the euro, which did not pan out. The day after the referendum, Britain’s rights and obligations would remain the same, as would the rule book for business. Champions of Brexit say all sides — from London to Brussels to Berlin — would have the incentive to agree a smooth transition.

Article 50 sets departing countries a two-year deadline to agree terms with a weighted majority of remaining EU states. But a comprehensive EU-UK trade deal would require unanimity and national ratification — giving parliaments a veto all the way down to the assembly for the 76,000 strong German-speaking community of Belgium.