The authoritative source for independent research on UK-EU relations

What is the backstop?

We’d be safely on the home straight by now – Withdrawal Agreement agreed and a political declaration on the future UK-EU relationship undergoing a final polish – were it not for one dastardly issue: ‘the backstop’. And its complexity only appears to grow, regardless of how much the negotiators try to reassure us of their proximity to a conclusion: 80%, 90%, 95%!

Northern Ireland is often associated with the word ‘intractable’. How true it is with Brexit and the backstop. And how unfortunate it is, to say the least, that the negotiations on a withdrawal deal could ultimately fail over what to do with this complicated small region of 1.8m people.

Or, to be more precise, what to do with the border of some 499km between Northern Ireland and Ireland that will, with Brexit, become the border between the UK and the EU.

Both the UK and EU have repeatedly pledged their intention to avoid seeing this boundary become a ‘hard border’. The question, of course, is how.

Both sides share a hope that this commitment will be met through the future UK-EU relationship. This enables them to put off tricky decisions and their practical working-out until some way down the line

For the form and substance of the future relationship still has to be negotiated, and it will not be in place until the end of the transition period (anticipated to be from 1 January 2021 at the earliest). There is no way of guaranteeing, at this stage, that any new UK-EU trade agreement(s) will actually manage to avoid a hard Irish border. As such, the prospect of an unspecified future relationship cannot offer meaningful reassurance to anyone in Northern Ireland or Ireland at the moment.

With this in mind, both the UK and the EU agree that there should be a ‘backstop’ arrangement in the Withdrawal Agreement. They view this like an insurance policy: something neither wish to have to call upon, but which would come into force if it is the only way of upholding their common pledge.  What they disagree about is what form that insurance policy should take.

For the EU, avoiding a hard Irish border is no easy task, especially if Brexit involves the UK being outside a customs union with the EU and leaving the internal market. Putting in place something specific for Northern Ireland has long been the EU position. This means that it does not force the whole of the UK into to a particular relationship with the EU; at the same time, however, it means that the unique circumstances of Northern Ireland are at the core of withdrawal negotiations.

By contrast, what we know from the recent four-point plan of the UK Prime Minister is that the UK government wants to land on a backstop that applies to the UK as a whole and that has as little consequence as possible. The UK is therefore seeking a slightly longer transition period allowing a little extra time – a few months – to square the circle: the UK being outside the EU’s internal market and customs union but still avoiding checks or controls on goods moving across the UK-EU border in Ireland.

It is also looking to a backstop arrangement that would involve the UK – and not just Northern Ireland – temporarily remaining in a customs union with the EU. Crucially, the UK insists that this arrangement would be either time-limited or allow for unilateral withdrawal. Both of these conditions make it insufficient, however, to constitute a stand-alone ‘backstop’ for the Irish border conundrum.

So, the negotiations continue. This explainer outlines the core pieces of information needed to understand the backstop discussions: the origins and need for a backstop, what has been agreed between the UK and EU so far, and what remain the current issues for negotiation.

Why is a backstop necessary?

Throughout the Brexit negotiations, the UK and the EU have recognized ‘the unique circumstances of the island of Ireland’. Such circumstances arise from the existence of the land border between the UK and Ireland, together with the peace process in Northern Ireland and the 1998 Belfast (Good Friday) Agreement on which it is founded.

The complexity of the challenge is seen in the fact that these two factors are closely connected: much of the conflict in Northern Ireland centred on the contested status of the Irish border, and the relatively frictionless nature of the border has been one of the greatest dividends of peace.

When the UK Prime Minister, Theresa May, on 29 March 2017 notified the President of the European Council, Donald Tusk, of the UK’s intention to withdraw from the EU, particular attention was drawn to the fact that the UK and the EU:

“have an important responsibility to make sure that nothing is done to jeopardise the peace process in Northern Ireland, and to continue to uphold the Belfast Agreement.”

May was clear: ‘We want to avoid a return to a hard border’ between Ireland and Northern Ireland.

The EU’s response had a similar focus. In April 2017, the European Council, in adopting guidelines for the negotiations, declared that the EU:

“has consistently supported the goal of peace and reconciliation enshrined in the Good Friday Agreement in all its parts, and continuing to support and protect the achievements, benefits and commitments of the Peace Process will remain of paramount importance.”

It added:

“In view of the unique circumstances on the island of Ireland, flexible and imaginative solutions will be required, including with the aim of avoiding a hard border, while respecting the integrity of the Union legal order.”

Shared UK and EU objectives on this subject were later set out in the oft-cited UK-EU Joint Report of December 2017 on the state of progress in the withdrawal negotiations. A first objective is that the Belfast (Good Friday) Agreement of 1998:

“must be protected in all its parts, and that this extends to the practical application of the 1998 Agreement on the island of Ireland and to the totality of the relationships set out in the Agreement”.

Second, they agree that UK withdrawal from the EU gives rise to ‘substantial challenges to the maintenance and development of North-South cooperation’ given the ‘significant extent’ to which it relies on ‘a common [EU] legal and policy framework’.

These commitments (alongside a third on supporting the all-island economy) were reiterated in Paragraph 49, which made the priority given to peace and the Irish border very clear:

“The United Kingdom remains committed to protecting North-South cooperation and to its guarantee of avoiding a hard border. Any future arrangements must be compatible with these overarching requirements.”

From Joint Report to Draft Protocol

The Protocol on Ireland/Northern Ireland attached to the draft Withdrawal Agreement is an effort to translate these commitments into legally binding text – one that would endure regardless of the outcome of still-to-come negotiations on the future UK-EU relationship. An initial version was published by the EU on 28 February 2018. A second version followed on 15 March 2018, before UK and EU negotiators on 19 March 2018 issued a revised draft of the Withdrawal Agreement which was colour coded to indicate the provisions on which there was at least some degree of agreement.

The draft Protocol on Northern Ireland/Ireland has a lengthy preamble noting, among other things, ‘that it is necessary to address the unique circumstances on the island of Ireland through a unique solution in order to ensure the orderly withdrawal of the United Kingdom from the Union’. The ‘unique solution’ is then set out in the main provisions of the Protocol.

Indeed, because it directly addresses the unique circumstances of Northern Ireland, much of it will have to apply come what may. This includes commitments to ‘no diminution of rights, safeguards and equality of opportunity’ as set out in the 1998 Agreement and to the continued operation of the Common Travel Area between Ireland and the UK.

The most contentious elements of the draft Protocol are primarily those relating to trade and regulations. The draft text outlines what the EU sees as necessary in this regard to meet the Joint Report commitment to avoid a hard border on the island of Ireland, including ‘physical infrastructure and related checks and controls’.

To avoid regulatory barriers to the movement of goods, the EU proposes a common regulatory area between the EU and the UK ‘in respect of Northern Ireland … in which the free movement of goods is ensured and North-South cooperation protected’.  And, to avoid customs procedures and controls, it proposes that Northern Ireland be ‘considered to be part of the customs territory of the Union’.

Further provisions would: maintain the island of Ireland as a single regulatory area for animal and plant health (as it currently is – hence the existing checks and controls on certain agricultural products entering Northern Ireland from Britain); maintain EU law in Northern Ireland on the production and marketing of agricultural and fisheries; and maintain the single electricity market on the island of Ireland. EU state aid rules are also to apply in respect of Northern Ireland.

The Protocol also sets out 14 ‘other’ areas in which north-south cooperation will be supported, before turning to governance arrangements that include a specialized UK-EU committee on the implementation of the Protocol and an ‘upon invitation and on a case-by-case basis’ decision-shaping role for the UK in EU bodies when discussing new and revised measures to be implemented in respect of Northern Ireland under the Protocol.

From an EU perspective, its proposed ‘NI backstop’ thus balances the requirement of avoiding a hard border with the need to retain the integrity of the customs union and – even though restricted to the free movement of goods – the EU internal market. It also, through specific arrangements for Northern Ireland, demonstrates flexibility and imagination by allowing part of a member state privileged access to certain core EU activities.

What the two sides agree upon

The proposed common regulatory area and customs union dimension of the ‘NI backstop’ met with strong resistance from the UK government. Nonetheless, there are several areas on which agreement has been reached (colour coded green) – common travel area, areas of north-south cooperation, specialised committee, subsequent agreement; or on which there is agreement on the ‘policy objective’ (colour coded yellow) – preamble, rights of individuals, single electricity market, state aid, safeguards.

The extent of this agreement shows that the need and broad scope of the backstop is not disputed. What remains to be agreed is the detail and ‘the right operational approach’, particularly in relation to the movement of goods.

On the same day that UK and EU negotiators issued the colour-coded draft of the Withdrawal Agreement, Theresa May wrote to Donald Tusk, President of the European Council, affirming that a backstop to address Northern Ireland’s ‘unique circumstances’ should be in the Withdrawal Agreement:

“If our future [UK-EU] partnership cannot completely resolve the issues in such a way as to meet our commitment on the border, I will want to explore additional specific solutions that can address the unique circumstances. I am committed to agreeing in the Withdrawal Agreement operational legal text for at least the so-called ‘backstop option’ set out in in the Joint Report, in parallel with discussions in these other scenarios.”

The covering statement to the draft Withdrawal Agreement is clear that there is a need for a backstop and it must be legally operative:

the negotiators agree that a legally operative version of the “backstop” solution for the border between Northern Ireland and Ireland, in line with paragraph 49 of the Joint Report, should be agreed as part of the legal text of the Withdrawal Agreement, to apply unless and until another solution is found.

Crucially, to be ‘legally operative’ there needs to be clarity around how and when the backstop’s provisions enter into force. The text of the draft Withdrawal Agreement does this by providing for the provisions of the Protocol to come into effect from the end of the transition period.

The text in the Protocol also shows that the UK and EU agree that the ‘backstop’ arrangements will remain in place ‘unless and until’ a future UK-EU agreement that avoids a hard Irish border enters into force.

Should a subsequent agreement between the Union and the United Kingdom which addresses the unique circumstances on the island of Ireland, avoids a hard border and protects the 1998 Agreement in all its dimensions, become applicable after the entry into force of the Withdrawal Agreement, this Protocol shall not apply or shall cease to apply, as the case may be, in whole or in part, from the date of application of such subsequent agreement and in accordance with that agreement.

The effect of this Protocol shows that disapplication of any provision of the backstop can only be brought about by agreement of the UK and the EU. Neither party can unilaterally remove the backstop or elements of it. The criteria for agreeing disapplication, however, have not been set out. In part this reflects that fact that both sides appear to have different interpretations of what a ‘hard border’ is.

The UK in the Joint Report recall a commitment to avoiding ‘any physical infrastructure or related checks and controls’ (paragraph 43), although subsequent statements have suggested that this is understood to be ‘at the border’ – so opening up the possibility of checks near or further away from the border. The EU, on the other hand, understands a hard border in much broader terms of trade friction, referring to, for example, non-tariff barriers to trade.

The persistence of such differences highlight the reasons why the decision to exit the terms of the backstop cannot be a unilateral one. It also highlights the need for clarity on the conditions for such an exit or a disapplication, and on the process.

Finally, in a Joint Statement issued by UK and EU negotiators on 19 June 2018, they also agree that the backstop must include trade and customs:

“[b]oth Parties recognise that the backstop on Ireland/Northern Ireland requires provisions in relation to customs and regulatory alignment in line with paragraph 49 of the Joint Report of December 2017”.

The UK: caught between conflicting commitments

The challenge for the UK government has been to square its commitments to Northern Ireland with its red lines on leaving the customs union and the single market. There is a zero-sum quality to some of these debates. Put simply: the closer the UK-EU relationship, the softer the Irish border can be; the more distant the UK-EU relationship, the harder the Irish border.

In attempting to avoid that hard Irish border, therefore, checks may come into play before goods enter the island of Ireland. This appears to posit a choice between checks on goods crossing the Irish border versus checks on goods crossing the Irish Sea.

Such a choice is politically loaded, to say the least. The idea of Northern Ireland having to choose between checks and controls on east-west trade and on north-south trade is one that throws enormous new significance upon the traditional unionist versus nationalist debate.

Compounding the situation is an unwillingness to see differentiated post-withdrawal arrangements within the UK, specifically on the grounds they would allegedly threaten the constitutional integrity of the UK. Reluctance has turned to open resistance, with the May government’s reliance on a confidence and supply agreement with the Democratic Unionist Party (DUP) becoming shaky.

However, paragraph 50 of the Joint Report implied that the UK government would be willing to see different arrangements for Northern Ireland, including regulatory divergence, if the devolved institutions so approved:

In the absence of agreed solutions, as set out in the previous paragraph, the United Kingdom will ensure that no new regulatory barriers develop between Northern Ireland and the rest of the United Kingdom, unless, consistent with the 1998 Agreement, the Northern Ireland Executive and Assembly agree that distinct arrangements are appropriate for Northern Ireland. In all circumstances, the United Kingdom will continue to ensure the same unfettered access for Northern Ireland’s businesses to the whole of the United Kingdom internal market.

It is not possible to put this into the Withdrawal Agreement because these are unilateral commitments on which only the UK government can deliver.

Unionists, particularly in Northern Ireland, fear that a ‘hard Brexit’ – with the UK outside a customs union with the EU and no longer formally aligned with the rules of the internal market – will lead to growing divergence between the UK and EU. This would most likely lead to the backstop being used, and thus the potential for new checks and controls on the movement of goods from the rest of the UK into Northern Ireland.

A backstop to a backstop?

It is the desire to avoid such differentiation and potential additional east-west checks and controls on the movement of goods (as noted above, checks and controls already exist on live animals and certain agricultural products) that has inspired the UK to seek a UK-wide backstop that would replace the NI-specific backstop in the Withdrawal Agreement.

This UK-wide backstop, however, would be time-limited, reflecting the need for the government to be able to assure Brexiteers that the UK will not be indefinitely ‘chained’ to the EU. There has also been political pressure on the UK government to insist that such a ‘UK-wide’ backstop include a mechanism allowing the UK to withdraw from it unilaterally.

The EU has accepted the idea of including in the Withdrawal Agreement a joint UK-EU commitment to negotiating a ‘UK-wide’ customs union backstop in the transition period. This is different, however, from putting an all-UK arrangement into the text of the Withdrawal Agreement itself – which is about the UK’s withdrawal from the EU, not the future relationship – although there have been some recent indications that the EU may be willing to agree to such an option. This would help assuage UK concerns about Northern Ireland’s position within the UK internal market if backstop arrangements came into force.

The whole premise of the Protocol on Northern Ireland/Ireland in the Withdrawal Agreement is, however, founded on ‘the unique circumstances of the island of Ireland’. The NI-backstop is designed to meet the specific commitments of the Joint Report particularly as they relate to the border between Ireland and Northern Ireland.

The EU has therefore consistently argued that any UK-wide backstop, particularly if it is time-limited, can only complement and not replace a ‘NI backstop’. A time-limited arrangement would not, by definition, provide the assurances necessary for the commitments to avoid a hard border to be upheld. It is for such reasons that the EU insists on a NI-specific backstop being agreed and included in the Withdrawal Agreement.

This is what is being referred to as ‘the backstop to the backstop’. The phrase is somewhat misleading, however, since technically a time-limited customs union arrangement from which one party could also unilaterally withdraw before the end of its intended duration would not constitute a backstop.


The prospect of any new checks or controls on the movement of goods across the Irish border lies at the heart of the ‘backstop’ problem. It is impossible to get around the fact that, the further the UK moves away from the EU’s customs arrangements and rules and regulations governing the movement of goods in the internal market, the greater the need for border controls.

If, after the transition period, the UK is no longer in a customs union with the EU and no longer subscribes to the four freedoms of the EU internal market, there will be a need for customs and regulatory checks between the UK and the EU. The EU has proposed in its version of the backstop that Northern Ireland can be considered effectively part of the EU customs union and its single market for goods, thus removing the need for checks and controls on the Irish border.

However, this would inevitably mean there would be a need for additional checks and controls on the movement of goods from the rest of the UK into Northern Ireland. Both sides have worked on proposals for ‘de-dramatising’ such controls, predominantly through the use of electronic means of processing and minimal checks on goods being conducted away from the border.

Adding to the complexity is the fact that neither the EU customs unions nor its internal market are static; they evolve, notably through new trade agreements and new or revised regulations. If a hard border is therefore to be avoided in the future, it is necessary for regulatory alignment between Northern Ireland and the EU to be maintained. For some, this is a challenge to Northern Ireland’s political position in the UK; for others it is an opportunity for Northern Ireland’s future economic position.

Unfortunately, and ironically, the political debate around the backstop epitomises the type of choice that was defused by the peace process it seeks to protect. A peaceful and prosperous Northern Ireland depends on protecting its integral closeness to both Britain and Ireland.

By Dr Katy Hayward, Reader in Sociology at Queen’s University Belfast and David Phinnemore, professor of European politics at Queen’s University Belfast.


The direction of travel for English devolution – a matter of perspective

Mr Yousaf’s conference challenge

Will support for Scottish independence go away?

Northern Ireland’s vicious cycle of governance failure

Destructive ambiguity – Northern Ireland, the Union and the Windsor Framework

Recent Articles