Sionaidh Douglas-Scott: What Happens to ‘Acquired Rights’ in the Event of a Brexit?

Sionaidh Douglas-ScottTwo recent UK Constitutional Law Association blogs (see here and here) have highlighted the importance of rights in the context of the UK’s referendum on EU membership, and indeed within EU law more generally.

However, one area of EU rights law where there still exists little information is that of acquired rights. In spite of being central to the Brexit debate, the topic of acquired rights is beset by confusion and misinformation. This is regrettable because any future lack of protection of rights currently guaranteed under EU law is one of the most serious risks of a UK withdrawal from the EU. While a recent House of Lords EU committee report on ‘The Process of Withdrawing from the EU’ asserted that ‘determining the acquired rights of the two million or so UK citizens living in other Member States, and equally of EU citizens living in the UK…would be a complex and daunting task,’ it did not elaborate further on the matter. This blog aims for further clarification, and the picture is not encouraging.

It is clear that EU law and the EU treaties are distinct from many other international treaties in the extent to which they give individuals rights, ‘which become part of their legal heritage’ (Case C-26/62, van Gend en Loos). Since the UK joined the (then) EEC in 1973, EU law has furnished British citizens with an immense array of rights and freedoms. But a crucial question of the Brexit debate is what happens to these rights if the UK withdraws from the EU? Post-withdrawal, EU law would cease to apply in the UK, meaning not only would the EU treaties cease to apply, but any national law implementing EU law would have to be repealed, amended, or possibly retained. So the legal source of many, or even most, of these rights would be removed

These rights presently take a number of forms. British citizens have used their free movement rights under EU law to move to other EU countries and to live, work and retire there. Other EU citizens have likewise moved to the UK. These citizens need to know how, and if, their rights are protected to understand fully the implications of a Brexit. However, the rights at issue are not only migratory in nature. British business enjoys all sorts of rights of freedom to trade within the EU, without tariff or non tariff barriers, as indeed do other EU traders with Britain. Investors and companies have long-term supply and procurement contracts, on the basis that the UK is a part of the EU. The EU Charter of Fundamental Rights is legally enforceable, carrying the same weight as the EU treaties. So it is a fundamental to know what would happen to all of these measures in the event of a Brexit.

Protection of rights in such situations concerns an area known as that of ‘acquired rights’ in legal terms. Acquired rights (sometimes also described as vested or executed) are those rights not automatically revoked if a treaty or law no longer applies. If acquired rights are recognised, then once a person/organisation has exercised them, they cannot be removed – even in the event of a change in the ultimate power over a country (e.g. a grant of independence, secession, or exit from the EU).

The crucial question therefore is whether rights already exercised under EU law (such as the rights of other EU citizens currently living and working in the UK, or of British nationals currently living and working elsewhere in the EU, without the need for a residence permit, work permit or visa) would be legally recognised as ‘acquired’, and still enforceable after a Brexit? Put differently, might the ECJ’s famous holding in van Gend, that EU law confers rights on Member State nationals that become part of their ‘legal heritage,’ actually imply that this legal heritage can outlast the legal provisions that created it? On this issue we find much confusion.

EU law

An obvious place to turn on this issue is EU law. Do EU treaties require that rights acquired under EU law be continued, should a state leave the EU? Art 50(3) TEU, which concerns withdrawal from the EU, provides:

 ‘the Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period. ’

But Article 50 makes no specific mention of acquired rights. Nor does any other provision in the EU Treaties set out any explicit rules on protection of acquired rights. There is no legal obligation under the EU treaties for them to be taken into account. This contrasts with some international treaties, such as the ECHR, or the Energy Charter Treaty, which provide specific protection for individuals’ acquired rights on termination of the treaty.

Of course, EU Law is not just a matter of treaty law, but also of general principles recognised as binding in EU law. While there is no general principle of EU law specifically protecting acquired rights, a principle of relevance is that of legal certainty, recognised as a general principle of law by the ECJ (see e.g. Case 74/74 CNTA (1975) ECR 533). Legal certainty has specific applications, such as non-retroactivity and legitimate expectations, which may be of some relevance. Yet it is unlikely that, in the event of Brexit, EU general principles of law could protect acquired rights within either UK courts, or those in another member state. On withdrawal, EU general principles would no longer be a justiciable source of law in the UK. And if an expat, for example, were to seek to assert their relevance in another EU state, the argument could be made that EU law did not apply to their situation as, being no longer EU citizens, they lacked a connecting factor with EU law.

International law

It is clearly advisable for the UK to negotiate protection of acquired rights as part of a Withdrawal Agreement with the EU. However, it is possible that there might be no Agreement, or alternatively that even an extensive agreement might fail to protect acquired rights adequately. If this happens, is international law capable of protecting acquired rights? Some commentators, particularly those, such as this Leave Alliance pamphlet, favouring Brexit (but also those active on expat Blogs who wish to assure their followers that they have nothing to fear in the case of a Brexit) believe that it can. And they cite Article 70 of the Vienna Convention on the Law of Treaties as relevant. However, I would be cautious in claiming international law as a clear source of protection for acquired rights.

Article 70.1(b) Vienna Convention provides that termination of an international treaty ‘does not affect any right, obligation or legal situation of the parties created through the execution of the treaty prior to its termination.’ The Institute of Economic Affairs suggested in Directions for Britain outside the EU (p. 82) that the effect of Article 70 is that ‘the impact of Britain leaving the EU will not be that great for those EU citizens already resident here or for British citizens living abroad’ although ‘The difference will be felt by those who move to a different state after British withdrawal.’ However, this is not altogether accurate. While a difference would be felt by those migrating after a UK withdrawal, the crucial point is that the reference to ‘the parties’ in Article 70 is a reference to the parties to the treaty – i.e. States. Article 70 does not directly address individual rights. The International Law Commission, in its commentary on the scope of the identically worded predecessor to Article 70.1(b) (Article 66 draft Vienna Convention) specifically rejected an interpretation that it gave rise to acquired rights:

‘… by the words “any right, obligation or legal situation of the parties created through the execution of the treaty”, the Commission wished to make it clear that paragraph l(b) relates only to the right, obligation or legal situation of the States parties to the treaties created through the execution, and is not in any way concerned with the question of the “vested interests” of individuals.’

Anthony Aust, author of Modern Treaty Law and Practice, emphasises (at p. 266) that the words ‘of the parties’ ‘are to make clear that the provision is not concerned with the question of the vested interests of individuals.’

So it would seem that the faith placed in the capacity of Article 70 Vienna Convention to protect acquired rights may well be misplaced.

If not the Vienna Convention, what about customary international law? There is some authority suggesting that, under customary international law, some treaty obligations continue to exist, protecting acquired rights notwithstanding the termination of a treaty. For example, in Certain German Interests in Polish Upper Silesia (1926), the Permanent Court of International Justice stated that ‘the principle of respect for vested rights … forms part of generally accepted international law.’ However, to the extent that acquired rights are recognised by customary international law, their scope is very narrow. For example Dörr and Schmalenbach, in their commentary on international law, assert (at p. 1207) that

‘Essentially the doctrine of acquired rights is confined in practice to private rights of individuals accrued under the municipal law and almost invariably occurred in the doctrine of State succession, investment law apart. Its extension to other rights of individuals is highly doubtful. For example, it cannot generally be said that rights occurring under treaties concerning the protection of human rights confer acquired rights to individuals that continue to exist even if the treaty is denounced. ’

Although some international lawyers (e.g. Rein Mullerson, International Law, Rights and Politics at p. 154) have argued that human rights treaties can bind successor states, (and this may be the case with the ECHR – see the 2009 case Bijelic v Montenegro and Serbia) in any event, most pressing issues of EU acquired rights are not strictly speaking human rights. They relate to EU citizens’ exercise of their free movement, whether to work or to trade elsewhere, and these are not usually classified as human rights, and are often established or elucidated in secondary legislation, rather than in a treaty in any case.

What is certainly clear is that international law does not treat all rights as worthy of respect as acquired rights, indeed it does not protect most rights as acquired rights. International law jurist, Pierre Lalive, writes (‘The Doctrine of Acquired Rights’ at p. 166):

‘However solemnly confirmed in international case law, notably by decisions of the World Court, the principle of respect for acquired rights in case of a cession of territory is subject to important limitations. First, the principle covers only certain rights, mainly individual private rights… As for subjective rights of a public or political character, they usually do not enjoy the protection granted to acquired rights. This is true, at least, in general international law.’

A distinction therefore exists between property and contractual rights (for example, ownership of a property in Spain, or a right not to have a work contract terminated) which are usually protected as acquired rights, and other rights (such as residence, healthcare rights and other benefits, as well as the freedom to work and trade, currently enjoyed by EU migrants) whose status is uncertain, to say the least.

Further, Jean-Claude Piris (former General Director of the Legal Service of the Council of the EU) has argued (in ‘Should the UK withdraw from the EU: legal aspects and effects of possible options’) that the idea of vested EU rights would lead to ‘absurd consequences’:

‘I would not think that one could build a new legal theory, according to which “acquired rights” would remain valid for millions of individuals … who, despite having lost their EU citizenship, would nevertheless keep its advantages for ever (including the right of movement from and to all EU Member States? Including the right to vote and to be a candidate in the European Parliament?). Such a theory would not have any legal support in the Treaties and would lead to absurd consequences.’


At present, we cannot know what might be negotiated in a Withdrawal Agreement, nor what the UK Government’s withdrawal strategy might be, nor indeed if the EU would be a hard bargainer, leading to negative economic effects for the UK. What should be clear is that, absent a Withdrawal Agreement which gives give clear protection of acquired rights, existing national, EU and international law does not offer a great deal of protection. So the content of the Withdrawal Agreement would be crucial. And in order to protect British citizens’ acquired rights in such an Agreement, reciprocity would be necessary (i.e. the UK would have to offer similar protections to those from other EU states). Otherwise UK citizens may sacrifice their current rights under EU law in the cause of British isolation.

Sionaidh Douglas-Scott, Anniversary Chair in Law, Queen Mary University of London

(Suggested citation: S. Douglas-Scott, ‘What Happens to ‘Acquired Rights’ in the Event of a Brexit?’, U.K. Const. L. Blog (16th May 2016) (available at