And yet the quarrels go on: The U.K. and the EU of now 27 nations are once again trading accusations and insults as they try to resolve rough spots in their relationship.
WHAT’S THE PROBLEM?
The current conflict centers on Northern Ireland, the only part of the U.K. that shares a land border with an EU member — Ireland.
While Britain was part of the EU's vast free trade single market, there were no barriers to people and goods crossing that border. The open frontier helped underpin the peace process that ended decades of Catholic-Protestant violence in Northern Ireland because if allowed the people there, whatever their identity, to feel at home in both Ireland and the U.K.
By taking the U.K. out of the EU’s economic order, Brexit creating new barriers and checks on trade. Both Britain and the EU agreed such checks could not take place on the Ireland-Northern Ireland border because of the risk to the peace process.
The alternative was putting a customs border in the Irish Sea — between Northern Ireland and the rest of the U.K. But the new sea border has brought headaches and red tape for businesses, and has riled Northern Ireland’s Protestant unionists, who say it weakens Northern Ireland’s place in the United Kingdom and threatens their British identity.
WHY IS UK-EU CONFLICT ERUPTING NOW?
Problems have been piling up since the U.K. left the EU's economic embrace, including the bloc's single market, at the end of 2020.
Under the divorce agreement, the British government was required to impose customs checks on goods entering Northern Ireland from the rest of the U.K. It has repeatedly postponed introducing them, to the annoyance of the EU.
Specific problems have emerged around agricultural and food products -- most prominently a looming ban on chilled meat products entering Northern Ireland from the rest of the U.K. that spurred headlines about a “sausage war.”
Opposition from Northern Ireland unionists to the deal has hardened. Jeffrey Donaldson, leader of Northern Ireland’s Democratic Unionist Party, said Tuesday that “if it is not replaced, then it will condemn Northern Ireland to further harm and instability."
Anger over the new arrangements helped fuel several nights of violence in Northern Ireland in April, largely in Protestant areas, that saw youths hurl bricks, fireworks and petrol bombs at police.
That has led the British government to argue that the Brexit deal itself — negotiated and agreed by the U.K. and the EU — is undermining the peace process.
WHAT DOES THE EU SAY?
The EU agrees that the Northern Ireland arrangements are not working well. On Wednesday, it offered proposals to ease the burden by cutting checks on food, plant and animal products by 80% and paperwork for transport companies in half.
On the eve of that move, the U.K. raised the stakes again, demanding the EU also remove the European Court of Justice as the ultimate arbiter of the Brexit agreement and instead agree to international arbitration.
The EU is highly unlikely to accept that. The bloc’s highest court is seen as the pinnacle of the EU single market, and Brussels has vowed not to undermine its own order.
Britain’s demand has led some in the EU to doubt Johnson’s government ever was sincere about sticking to the agreement.
WHAT WILL HAPPEN NEXT?
The EU and the U.K. say they will hold several weeks of “intensive” talks on the latest proposals.
The talks could lead to a breakthrough or a breakdown; the signals are mixed. On the one hand, there have been moments during Brexit when the U.K. threatened to walk away without a deal, only to compromise at the last minute. This could be another one.
But if the British government sticks to its insistence on ruling out a role for the European court, it is hard to see room for compromise.
In that case, Britain says it will trigger an emergency break clause that allows either side to suspend the Brexit agreement if it is causing exceptional hardship. Such a move would infuriate the EU, which is likely to respond with legal action and possibly economic sanctions against the U.K.
It could spiral into an all-out trade war — one that is likely to hit the U.K. economy harder than that of the much bigger bloc.
Northern Ireland's Democratic Unionists, meanwhile, are threatening to collapse the power-sharing Belfast government if the deal is not ripped up, a move that would trigger elections and plunge the region into fresh uncertainty.
Follow AP’s coverage of post-Brexit developments at https://apnews.com/hub/Brexit