How Could UK Rejoin EU?

Brexit was legally complex. Rejoining would be even harder. Here is a sober look at the political, legal, and diplomatic path back.

When the UK left the European Union on 31 January 2020, it became the first member state ever to invoke Article 50 of the Treaty on European Union and complete a withdrawal. The process took nearly four years of negotiation, produced a 1,246-page Withdrawal Agreement, and fractured British politics in ways that have not yet fully healed. The question of whether the UK could or should reverse course has never fully disappeared from public debate. But the honest answer is that rejoining would be neither quick nor automatic. It would require a formal accession process that is more demanding than the terms Britain left under, and would demand political will on a scale that does not yet exist.

There is no special return route

One of the most widely misunderstood points about rejoining is that there is no "fast track" or reversal mechanism. Article 50 allowed the UK to leave; there is no Article equivalent for returning. If the UK wished to rejoin, it would have to apply under Article 49 of the Treaty on European Union, which is the standard accession route used by every country that has ever joined the EU. That process was designed for states with no prior membership, and it makes no formal distinction for former members. The UK would join the queue alongside any other applicant nation.

This is not merely a procedural inconvenience. It has profound practical consequences. Article 49 requires a unanimous vote of all existing EU member states to approve accession. It requires the applicant country to negotiate its terms of entry, chapter by chapter, across dozens of policy areas. And it requires ratification by every member state's parliament, meaning a single national legislature anywhere from Tallinn to Lisbon could block UK membership. Currently, the EU has 27 members. Unanimity is a very high bar.

"There is no return lever. Rejoining means applying as if for the first time."

The formal steps to membership

1. Political decision and application
The UK government formally applies for EU membership. This requires domestic political consensus, most likely including a referendum mandate or a substantial parliamentary majority, before Brussels would take the application seriously.

2. European Commission opinion
The Commission assesses the UK's readiness across the Copenhagen Criteria: stable democratic institutions, a functioning market economy, and the capacity to adopt the full body of EU law (the acquis communautaire).

3. Accession negotiations
Negotiations open on each chapter of the acquis. The UK would need to demonstrate alignment or agree to specific commitments in areas including competition law, state aid, financial services regulation, and fishing rights.

4. Unanimous Council approval
All member states must agree to admit the UK. Any single country can veto membership. This is the most politically exposed stage of the process.

5. Ratification
Every member state's national parliament (and in some cases regional parliaments, as with Belgium) must ratify the accession treaty. The European Parliament must also give its consent.

6. Accession
The UK formally becomes a member state again. Optimistic estimates put the minimum timeline at five to ten years from application to membership, assuming smooth negotiations.

The terms would not be the same

This is perhaps the most politically uncomfortable reality for pro-rejoin campaigners to acknowledge. When the UK was a member, it held a series of opt-outs and special arrangements that were negotiated over decades and in some cases granted as concessions to prevent the country from leaving. These included the UK rebate on budget contributions, opt-outs from the Schengen Area of passport-free travel, and an opt-out from the euro. None of these arrangements would automatically apply to a rejoining UK. They would have to be renegotiated from scratch, and the EU has shown little appetite to offer bespoke arrangements to applicant states in recent accession rounds.

In practice, this means a rejoining UK would almost certainly be required to commit to adopting the euro at some future point as joining the eurozone is now a standard condition of EU membership for new entrants, though the timeline can be negotiated. It would be expected to participate in Schengen, or at minimum to accept that it cannot stay outside it indefinitely. And it would contribute to the EU budget without the rebate that Margaret Thatcher secured in 1984. These are not small concessions. They would define the terms of any political debate about rejoining.

The obstacles are as much political as legal

Domestic politics
No major UK party currently supports EU membership. Building a governing coalition around rejoining would require a significant shift in public opinion and party policy.

The euro question
New members must commit to adopting the euro. Public support for replacing the pound is very low in the UK. This is the single largest domestic sticking point.

EU appetite
The EU has its own enlargement priorities, including Western Balkans, Ukraine, Moldova. A UK application would compete for political bandwidth and diplomatic energy.

Veto risk
Individual member states with grievances, such as over fishing, financial regulation, or historical disputes, could block or delay accession to extract concessions.

What a more realistic near-term path looks like

Most analysts who have examined this question closely argue that full membership is a distant prospect, but that there are intermediate steps the UK could pursue in the meantime. A customs union arrangement, similar to Turkey's relationship with the EU, would eliminate many of the trade frictions created by Brexit without requiring political union. A single market relationship, like Norway's through the European Economic Area, would restore free movement of goods and services but would also require accepting free movement of people. This was the issue that drove much of the Leave vote in 2016. Neither of these is membership, but both would represent a significant rapprochement.

The UK government since 2024 has pursued a "reset" of relations with the EU, securing agreements on defence cooperation, youth mobility, and veterinary standards. This is closer collaboration than existed immediately after Brexit, but it falls far short of market integration. It does, however, suggest that incremental steps are politically achievable even when full membership is not.

A note on democratic legitimacy

Most constitutional scholars agree that if a future UK government wished to apply for EU membership, it would need either a referendum result in favour of rejoining or an exceptionally clear general election mandate. The 2016 referendum result, while not legally binding, created a political expectation that a decision of this magnitude should be put to the public directly. Any government that attempted to rejoin without such a mandate would face severe legitimacy challenges, regardless of the formal legal position.

Conclusion: possible, but not soon

The UK could rejoin the European Union. The legal route exists and is clear. But it would take at minimum decades from any formal application, would require accepting terms substantially less favourable than those the UK held before 2020, and would demand a level of sustained political will and public consensus that is nowhere close to existing today. The more probable trajectory is one of gradual normalisation, closer cooperation on specific issues, perhaps a deeper trade relationship, rather than a return to the negotiating table for full membership. For those who want the UK back inside the EU, the honest message is that the work begins not in Brussels, but in changing minds at home. It is therefore our view that the UK is unlikely to rejoin the EU within most people's lifetimes.