With the exit door unlocked, the nature of EU membership is transformed

Article 50 of the Treaty of Lisbon is an instrument of destruction. Courtesy of the EU's exit clause, the UK's membership of the bloc will end at 23:00 GMT today, and the laws underpinning supply chains, diplomatic clout and individual rights accumulated over years will be scythed clean through.

With destruction can come invention, however. The 540-page Withdrawal Agreement, which comes into force at that same moment, the product of more than two years' painstaking and turbulent negotiation, is a remarkable feat of lawmaking.

Brexit's impact on the economics and politics of the UK and the EU have been well probed. Its more subtle legacy as a moment of constitutional creation is less well explored.

David Cameron warned prior to the 2016 referendum that leaving would be a "leap in the dark." So it seemed on the morning on June 24, as a void opened under the certainty of membership. "There will be no legal vacuum," promised European Council President Donald Tusk in his first remarks at dawn. The prospect of a messy breakup would linger for years.

The five-clause framework offered by Article 50 was fleshed out into a fully-formed exit manual that plugs gaps that had scarcely been considered in the referendum. How to bring British disputes being heard before the EU's top court to a tidy end? What to do with EU citizens' data held on British soil — or European nuclear waste? How to settle up financial liabilities stretching 50 years into the future, and for what in return?

The concepts that came to dominate British politics — "sequencing," "settled status," "backstop," "transition" — would not be conceived for months after the vote. "The British are discovering, as we are, day after day, new problems," European Commission President Jean-Claude Juncker remarked early in the talks.

These were not mere administrative challenges, but raised profound questions of European law. How much could be achieved within the two-year period? Was a transition period even legally possible? (Veterans of the European Parliament thought not; see here). How to give effect to the jurisprudence of the EU Court of Justice in a non-member state? What models of future relationship could be on the table? And could the process be stopped unilaterally? (The Luxembourg court said yes, against the arguments of the EU executive's legal service; see here).

On the UK side too, a similar pile of constitutional riddles awaited. What role did Parliament have in the triggering of Article 50? (An essential one, said the Supreme Court late last year). And how could EU law be unwound from the domestic statute book without unleashing chaos? (The EU (Withdrawal) Act, and vast "Henry VIII powers" for ministers to make amendments at speed, although the chaos may yet appear).

The Withdrawal Agreement "is an achievement and justifies the care that we took in drafting Article 50, and the political decision to include a secession clause in the treaty," said Andrew Duff, a former EU lawmaker and fellow at the European Policy Centre in Brussels. "It has worked quite well in circumstances I had not foreseen — that the departing country hadn't the faintest idea of why it wanted to leave or where it wanted to be after it had left."

Escape is possible

The terse five clauses that make up Article 50 meant referendum campaigners were free to paint Brexit as a fantasy of leaping free, or as a catastrophic tumble off a cliff. But the exit manual produced through the British experiment would render any future secession from the EU a more procedural affair, with calculable costs and a predictable landing zone. Is releasing such a text into the world not a dangerous thing?

There's no sign of a queue, for sure: Brexit may not have happened yet, but the UK's labored process invited ridicule and engendered divisive political turmoil, while the economic cost is already visible. The UK's final trade agreement with the EU will inevitably leave it with less influence and worse market access to the bloc.

The UK's Withdrawal Agreement, moreover, may be of somewhat limited use for other member states, as the country is neither a eurozone member, using the single currency, nor part of the Schengen Area borderless travel zone.

Yet the focus on whether any particular state may opt to follow the British — an understandable preoccupation of negotiators in Brussels — risks overlooking the fact that regardless, the nature of EU membership will, as of tonight, have subtly shifted.

With a well-defined exit procedure, it will be far harder for the bloc's other national leaders to argue that their country has no realistic chance of wrestling free (or, for that matter, to paint exit as a romantic dash for freedom). "It shows the EU is not a prison," said Agata Gostyńska-Jakubowska of the Centre for European Reform. "You don't have to be locked in forever."

Strengthened core

The desire to ensure no further departures will be overwhelming. And yet, states such as Hungary and Poland that have repeatedly clashed with the EU executive over the rule of law, a fundamental principle of the bloc, may well find themselves invited to follow the British example if they fail to reform, Gostyńska-Jakubowska said. "Someone could point to them and say, if you're not happy, there's a legal procedure allowing you to get rid of those constraints."

The existence of a blueprint for an orderly way out may also strengthen the hands of those wishing to see a federalized Europe, with a more integrated core and a looser circle of associated states.

"In a perverse way, despite the fact the departure left everyone [in the bloc] weaker and poorer, the exercise itself has strengthened the constitution of the EU," Duff said. "It's not fair to trap a state in a polity that is developing in a direction that hadn't been presaged or welcomed."