Below is the full text of the dissenting judgement given by Lord Carnwarth in the Supreme Court’s response to the Article 50 case. The full judgments, including the majority judgment against the Government, can be found here.
243. For the reasons given by Lord Reed, I would have allowed the appeal by the Secretary of State in the main proceedings. In view of the importance of the case, and the fact that we are differing from the Divisional Court and the majority in this court, I shall add some comments of my own from a slightly different legal perspective. I agree with the majority judgment in respect of the Northern Irish cases and the other devolution issues.
244. At the heart of the case is the classic statement of principle by Lord Oliver in the Tin Council case (JH Rayner (Mincing Lane) Ltd v Department of Trade and Industry  2 AC 418):
“… as a matter of the constitutional law of the United Kingdom, the Royal Prerogative, whilst it embraces the making of treaties, does not extend to altering the law or conferring rights upon individuals or depriving individuals of rights which they enjoy in domestic law without the intervention of Parliament …” (Lord Oliver pp 499E-500D)
245. In the Tin Council case Lord Oliver was speaking only of the “making of treaties”, not withdrawal. Lord Templeman had earlier made clear that the prerogative enables the Government to “negotiate, conclude, construe, observe, breach, repudiate or terminate a treaty …” (p 476F-H). However, there was no discussion of how the classic statement might need modification or development in the context of termination or withdrawal. In principle the same basic rule should apply. Just as the Executive cannot without statutory authority create new rights or obligations in domestic law by entering into a treaty, so it cannot by termination of a treaty take away rights or obligations which currently exist. However, that tells one nothing about the process by which this result is to be achieved, nor at what stage of that process the intervention of Parliament is required.
246. Precedents are hard to find. Counsel have taken us on an interesting journey through cases and legal sources from four centuries and different parts of the common law world. The only example we were shown of withdrawal from a treaty was a recent decision of the Canadian Federal Court: Turp v Ministry of Justice & Attorney General of Canada 2012 FC 893. That was an unsuccessful challenge by the executive to the use of its prerogative powers to withdraw from the Kyoto Protocol on Climate Change, against the background of a statute (passed against the opposition of government) requiring the preparation of plans giving effect to the Protocol. On its face it is a striking example of the use of the prerogative to frustrate the apparent intention of Parliament as expressed in legislation. However, the authority is of limited assistance in the present context, since it had been held in a previous case (Friends of the Earth v Canada (Governor in Council), 2008 FC 118) that the obligations under the statute were not justiciable in the domestic courts.
247. In the end the search through the authorities tells one little that is not sufficiently expressed by the classic rule. It also confirms the lack of any direct precedent for withdrawal from a treaty previously given effect in domestic law, let alone one which has played such a vital part in the development of our laws over more than 40 years. However, lack of precedent is not a reason for inventing new principles, nor is there a need to do so. The existing principles correctly applied provide a clear and coherent framework for effective resolution of all the competing considerations, including the referendum result.
The balance of power
248. In considering that framework it is important to recognise the sensitivity in our constitution of the balance between the respective roles of Parliament, the Executive and the courts. The Divisional Court saw this principally in binary terms: the Executive versus Parliament. Under the general heading, “the sovereignty of Parliament and the prerogative powers of the Crown”, they referred on the one hand to “the most fundamental rule that the Crown in Parliament is sovereign” (para 20), and on the other to the “general rule” that “the conduct of international relations and the making and unmaking of treaties” are “matters for the Crown in the exercise of its prerogative powers” (para 30), the balance between the two being as explained by Lord Oliver in the Tin Council case (paras 32-33).
249. Although the Tin Council principles as such are not in doubt, they are only part of the story. It is wrong to see this as a simple choice between Parliamentary sovereignty, exercised through legislation, and the “untrammelled” exercise of the prerogative by the Executive. Parliamentary sovereignty does not begin or end with the Tin Council principles. No less fundamental to our constitution is the principle of Parliamentary accountability. The Executive is accountable to Parliament for its exercise of the prerogative, including its actions in international law. That account is made through ordinary Parliamentary procedures. Subject to any specific statutory restrictions (such as under the Constitutional Reform and Governance Act 2010), they are a matter for Parliament alone. The courts may not inquire into the methods by which Parliament exercises control over the Executive, nor their adequacy.
The FBU case
250. Defining the proper boundaries between the respective responsibilities of Parliament, the Executive and the courts lay at the heart of the dispute in the FBU case (R v Secretary of State for the Home Department Ex p Fire Brigades Union  2 AC 513). That case concerned statutory provisions (under the Criminal Justice Act 1988) providing for compensation for criminal injuries, intended to replace a previous non-statutory scheme established under the prerogative. Section 171 provided that the new scheme should come into force on “such day as the Secretary of State may by order … appoint”. No such date was appointed, but instead after some years the Secretary of State announced that a new non-statutory scheme would be introduced, which was inconsistent with the scheme provided for by the Act. The House of Lords held by 3-2 that this action was an abuse of power and so unlawful. In the leading judgment Lord Browne-Wilkinson noted that the new scheme was to be brought into effect –
“… at a time when Parliament has expressed its will that there should be a scheme based on the tortious measure of damages, such will being expressed in a statute which Parliament has neither repealed nor (for reasons which have not been disclosed) been invited to repeal.
…, it would be most surprising if, at the present day, prerogative powers could be validly exercised by the executive so as to frustrate the will of Parliament expressed in a statute and, to an extent, to pre-empt the decision of Parliament whether or not to continue with the Statutory scheme even though the old scheme has been abandoned. It is not for the executive … to state as it did in the White Paper (paragraph 38) that the provisions in the Act of 1988 ‘will accordingly be repealed when a suitable legislative opportunity occurs.’ It is for Parliament, not the executive, to repeal legislation …” (p 552D-E)
“By introducing the tariff scheme he debars himself from exercising the statutory power for the purposes and on the basis which Parliament intended. For these reasons, in my judgment the decision to introduce the tariff scheme at a time when the statutory provisions and his power under section 171(1) were on the statute book was unlawful and an abuse of the prerogative power.” (p 554G)
The minority, by contrast, regarded the majority’s decision (in Lord Keith’s words – p 544) as “a most improper intrusion into a field which lies peculiarly within the province of Parliament”.
251. In a recent article (A dive into deep constitutional waters: article 50, the Prerogative and Parliament (2016) 79(6) MLR 1064-1089), Professor Gavin Phillipson considers some lessons from that decision for the present case. As he points out (ibid p 1082), the apparently fundamental difference of approach between majority and minority came down ultimately to a narrow issue of statutory construction of section 171: whether the section imposed no duty owed to the public (p 544F per Lord Keith), or rather, as the majority thought (p 551D, per Lord Browne Wilkinson), it imposed a continuing obligation on the Secretary of State to consider whether to bring the statutory scheme into force, which was frustrated by implementation of the inconsistent non-statutory scheme.
252. Professor Phillipson also draws attention to the important observations by Lord Mustill on the balance between the three organs of the state, and in particular the means by which Parliament exercises control of the Executive, not restricted to legislative control. Although stated in a minority judgment, the underlying principles are not I believe controversial. Lord Mustill said:
“It is a feature of the peculiarly British conception of the separation of powers that Parliament, the executive and the courts each have their distinct and largely exclusive domain. Parliament has a legally unchallengeable right to make whatever laws it thinks right. The executive carries on the administration of the country in accordance with the powers conferred on it by law. The courts interpret the laws, and see that they are obeyed. This requires the courts on occasion to step into the territory which belongs to the executive, not only to verify that the powers asserted accord with the substantive law created by Parliament, but also, that the manner in which they are exercised conforms with the standards of fairness which Parliament must have intended. Concurrently with this judicial function Parliament has its own special means of ensuring that the executive, in the exercise of delegated functions, performs in a way which Parliament finds appropriate. Ideally, it is these latter methods which should be used to check executive errors and excesses; for it is the task of Parliament and the executive in tandem, not of the courts, to govern the country…” (p 567D-F, emphasis added)
253. Lord Mustill went on to comment on the development over the previous 30 years of court procedures to fill gaps where the exercise of such “specifically Parliamentary remedies” has been perceived as falling short, and “to avoid a vacuum in which the citizen would be left without protection against a misuse of executive powers”. He thought these judicial developments were welcome but not without risks:
“As the judges themselves constantly remark, it is not they who are appointed to administer the country. Absent a written constitution much sensitivity is required of the parliamentarian, administrator and judge if the delicate balance of the unwritten rules evolved (I believe successfully) in recent years is not to be disturbed …” (p 567H)
254. Professor Phillipson comments:
“… the British constitution works most effectively when parliamentary and judicial forms of control and accountability, rather than being framed as antagonistic alternatives, or mutually exclusive directions of travel, work together, but with clearly defined, differentiated and mutually complementary roles.” (p 1089)
255. That observation is particularly pertinent having regard to the debate which took place on the opposite side of Parliament Square on the last day of the hearing in the Supreme Court. That led to the motion, passed by a large majority of the House of Commons, the terms of which have been set out by Lord Reed (para 163). In particular, it recognised that it is “Parliament’s responsibility to properly scrutinise the Government while respecting the decision of the British people to leave the European Union”, and ended by “call(ing) on the Government to invoke article 50 by 31 March 2017”. Of course the House of Commons is not the same as “the Queen in Parliament”, whose will is represented exclusively by primary legislation. However, the motion lends support to the view that, at least at this initial stage of service of a notice under article 50(2), the formality of a Bill is unnecessary to enable Parliament to fulfil its ordinary responsibility for scrutinising the government’s conduct of the process of withdrawal.
Application of the principles to the present case
256. The logical starting point for consideration of the present case is the power which is in issue: that is, the power under article 50 of the Lisbon treaty to initiate the procedure for withdrawal by a decision in accordance with our “constitutional requirements”, followed by service of a notice. The existence of that power in international law is not in doubt. The issues for the court are, first, who has the right under UK constitutional principles to exercise it, and, secondly, subject to what constitutional requirements. As to the first, under Tin Council principles the position is clear. In the absence of any statutory provision to the contrary, the power to make or withdraw from an international treaty lies with the Executive, exercising the prerogative power of the Crown. As to the second, it is necessary to consider whether that power is subject to any restrictions by statute, express or implied, or in the common law.
257. In agreement with Lord Reed, and for the same reasons, I find no such restrictions in the EU statutes. I agree with Mr Eadie that this issue must be considered by reference to the statutory scheme as it exists at the time the power in question is to be exercised. The 1972 Act of course provided the framework for what followed. But I find it illogical to search in that Act for a presumed Parliamentary intention in respect of withdrawal, at a time when the treaty contained no express power to withdraw, and there was no reason for Parliament to consider it. The 1972 Act did not remove the Crown’s treaty-making prerogative in respect of European matters, whether expressly or by implication (as under the De Keyser principle: majority judgment para 48). No-one doubts the power of the Executive in 2008 to enter into the Lisbon Treaty, including article 50.
258. The critical issue is how Parliament dealt with that matter for the purposes of domestic law. In the 2008 Act Parliament recognised the Lisbon treaty (including article 50) by its inclusion in the treaties listed in section 1 of the 1972 Act. Thereafter it became (by virtue of 1972 Act section 2(1)) part of the statutory framework “in accordance with” which, and therefore subject to which, any rights and obligations derived from EU law by virtue of that Act were to be enjoyed in domestic law. Unlike other powers in the treaty, the 2008 Act did not impose any restriction on the exercise of article 50 by the Executive. That position was confirmed by the 2011 Act, which made specific reference to article 50(3) but placed no restriction on article 50(2). There the matter rests today.
259. Turning to the common law, the Tin Council rule is simple and uncontroversial: the prerogative does not extend “to altering the law or conferring rights upon individuals or depriving individuals of rights which they enjoy in domestic law without the intervention of Parliament”. Judged by that test the answer again is clear. Service of an article 50(2) notice will not, and does not purport to, change any laws or affect any rights. It is merely the start of an essentially political process of negotiation and decision-making within the framework of that article. True it is that it is intended to lead in due course to the removal of EU law as a source of rights and obligations in domestic law. That process will be conducted by the Executive, but it will be accountable to Parliament for the course of those negotiations and the contents of any resulting agreement. Furthermore, whatever the shape of the ultimate agreement, or even in default of agreement, there is no suggestion by the Secretary of State that the process can be completed without primary legislation in some form.
260. This analysis was in substance adopted by Maguire J in the McCord proceedings, in line with the submissions of the Attorney General for Northern Ireland (repeated in this court). He said:
“In the present case, it seems to the court that there is a distinction to be drawn between what occurs upon the triggering of article 50(2) and what may occur thereafter. As the Attorney General for Northern Ireland put it, the actual notification does not in itself alter the law of the United Kingdom. Rather, it is the beginning of a process which ultimately will probably lead to changes in United Kingdom law. On the day after the notice has been given, the law will in fact be the same as it was the day before it was given. The rights of individual citizens will not have changed – though it is, of course, true that in due course the body of EU law as it applies in the United Kingdom will, very likely, become the subject of change. But at the point when this occurs the process necessarily will be one controlled by parliamentary legislation, as this is the mechanism for changing the law in the United Kingdom.” (para 105)
261. The Divisional Court (para 17) took a different approach. They in effect adopted the analysis proposed by Lord Pannick, taking account of the agreed (albeit possibly controversial) assumption that the article 50(2) notice is irrevocable. On that footing, even if it has no immediate effect, it will lead inexorably to actual withdrawal at latest two years later (subject to agreement to defer). Lord Pannick drew the analogy of a trigger being pulled (written case para 11-12):
“… it is the giving of the notice which triggers the legal effects under article 50(3). Those effects are that once notification is given, ‘[t]he Treaties shall cease to apply to the state in question’, from the date of a withdrawal agreement, or – if no such agreement is reached – at the latest within two years from notification, unless an extension of time is unanimously agreed by the European Council and the member state concerned. Notification is … the pulling of the trigger which causes the bullet to be fired, with the consequence that the bullet will hit the target and the Treaties will cease to apply.”
262. Lord Pannick’s trigger/bullet analogy is superficially attractive, but (with respect) fallacious. A real bullet does not take two years to reach its target. Nor is its progress accompanied by an intense period of negotiations over the form of protection that should be available to the victim by the time it arrives. The treaties will indeed cease to apply, and domestic law will change; but it is clearly envisaged that the final form of the changes will be governed by legislation. As the Secretary of State has explained, the intention is that the legislation will where possible reproduce existing European-based rights in domestic law, but otherwise ensure that there is no legal gap.
263. Although there is no evidence from any government witness on the intended role of Parliament, we were shown without objection or contradiction the statement made by the Secretary of State to Parliament on 10 October 2015 (Hansard Vol 615). Having described the “mandate” for Britain to leave European Union as “clear, overwhelming and unarguable”, he explained the government’s plans for a “great repeal Bill”:
“We will start by bringing forward a great repeal Bill that will mean the European Communities Act 1972 ceases to apply on the day we leave the EU … The great repeal Act will convert existing European Union law into domestic law, wherever practical. That will provide for a calm and orderly exit, and give as much certainty as possible to employers, investors, consumers and workers…
In all, there is more than 40 years of European Union law in UK law to consider, and some of it simply will not work on exit. We must act to ensure there is no black hole in our statute book. It will then be for this House – I repeat, this House – to consider changes to our domestic legislation to reflect the outcome of our negotiation and our exit, subject to international treaties and agreements with other countries and the EU on matters such as trade …”
264. On the assumption that such a Bill becomes law by the time of withdrawal, there will be no breach of the rule in its classic form. The extent to which existing laws are changed or rights taken away will be determined by the legislation. Ultimately of course that result depends on the will of Parliament; it is not in the gift of the executive. But there is no basis for making the opposite assumption. Lord Pannick’s argument in effect requires the classic rule to be reformulated: “the prerogative does not extend to any act which will necessarily lead to the alteration of the domestic law, or of rights under it, whether or not that alteration is sanctioned by Parliament”. We were shown no authority to support a rule as so stated, nor any principled basis for the court to invent it. In any event, that process, like the service of the article 50 notice, will be subject to Parliamentary scrutiny in whatever way Parliament chooses. It will be for Parliament and the Executive acting in partnership to determine the timing and content of the legislative programme.
Pre-empting the will of Parliament
265. One possible answer to the analysis in the previous paragraph is that it would involve the Executive unlawfully “frustrating” or “pre-empting” the will of Parliament. This point is touched on in the majority judgment by reference in particular to the Lord Browne-Wilkinson’s statements in the FBU case (see para 250 above). They are said to establish the principle that ministers cannot “frustrate” the purpose of a statute “for example by emptying it of content or preventing its effectual operation”; and that it is –
“… inappropriate for ministers to base their actions (or to invite the court to make any decision) on the basis of an anticipated repeal of a statutory provision as that would involve ministers (or the court) pre-empting Parliament’s decision whether to enact that repeal.” (majority judgment para 51)
266. As I understand the majority judgment, however, this line of argument does not ultimately form part of their reasoning, in my view rightly so. In the first place, the FBU case was case about abuse, not absence, of power. There was no doubt as to the existence of the prerogative power. But it was held to be an abuse to use it for a purpose inconsistent with the will of Parliament, as expressed in a statute which had it had neither repealed nor been invited to repeal. Such issues do not arise in this case. The Miller respondents base their case unequivocally on absence of a prerogative power to nullify the statutory scheme set up by the 1972 Act, rather than abuse (see Lord Pannick’s response to Lord Reed: Day 2 Transcript, p 158, lines 8-25).
267. Further, Lord Browne-Wilkinson was not purporting to lay down any general principle about the relevance of future legislation in relation to the exercise of the prerogative. His comments were directed to the facts of the particular case, in which the new scheme was being introduced without any reference at all to Parliament. Similar arguments in the present case would have to be seen in a quite different context, which (as Lord Pannick accepts) would include the 2015 Act and the referendum result. It is one thing, as in the FBU case, to use the prerogative to introduce a scheme which is directly contrary to an extant Act, and which Parliament has had no chance consider. It is quite another to use it to give effect to a decision the manner of which has been determined by Parliament itself, and in the implementation of which Parliament will play a central role. In such circumstances talk of frustrating or pre-empting the will of Parliament would be wide of the mark. Conversely, it would be wrong to assume (as the majority appears to do: para 91) that the courts would necessarily have been powerless in the (politically inconceivable) event of the Executive initiating withdrawal entirely of its own motion, or even in defiance of a referendum vote to remain.
Protection of individual interests
268. I would not wish to leave the case without acknowledging the important submissions made by the other respondents and interveners, particularly as to the scale and significance of the interests which will be affected by withdrawal. It is not clear, however, how a requirement for statutory authority for the article 50(2) notice will do anything to safeguard those interests, nor indeed to advance the process of Parliamentary scrutiny which will ultimately be critical to their protection.
269. I take as representative the cases for the third and fourth respondents, presented by Ms Mountfield QC and Mr Gill QC. Their submissions provide vivid illustrations of the variety of ways in which individual and group interests will be profoundly affected by implementation of the decision to leave the EU. Ms Mountfield for example provides a detailed breakdown of “fundamental” and “nonreplicable” EU citizenship rights. The list starts with the “fundamental status” of EU citizenship (Citizens’ Directive 2004/38/EC preamble), leading to more specific rights, such as the right to move, reside, work and study throughout the member states, the right to vote in European elections, the rights to diplomatic protection, and the right to equal pay, and to non-discriminatory healthcare free at the point of use. She categorises the government’s case as an assertion of –
“untrammelled prerogative power to do away with the entire corpus of European law rights currently enjoyed under UK law, and render a whole suite of constitutional statutes meaningless, without any Parliamentary authority in the form of a statute.”
While there is no reason to question her account of the profound effect of the prospective changes, I do not for the reasons already given accept that this can be describe as “untrammelled” use of executive power, nor that the control of Parliament will be improperly bypassed. Nor does she explain how that impact will be mitigated by a statute which does no more than authorise service of the notice.
270. Similar arguments are made by Mr Gill for the fourth respondents (the AB parties). They are representative, among others, of the very large numbers of EEA nationals and their children living in this country, whose rights to continued residence will be threatened unless adequate arrangements are made to protect them. Mr Gill refers in particular to the important right under the Citizens’ Directive for those who have lived in the UK for five years to apply for citizenship in the following year, a right which will be lost on withdrawal. Section 7 of the Immigration Act provides that a person shall not require leave to enter or remain in the United Kingdom “in any case in which he is entitled to do so by virtue of an enforceable EU right”.
271. Typical is Mrs KK, a Polish national resident and working here since 2014, married to a third country national, with a Polish national child born in the UK in 2015. She feels “in a complete state of limbo” having received no assurance from the Secretary of State as to what her status will be during and after the withdrawal negotiations, nor how her husband and child will be affected. Such people, says Mr Gill, will have made life-changing decisions and moved permanently to the UK with the ultimate intention of acquiring permanent residence. They may also find themselves exposed to criminal liability under the Immigration Act 1971 if their status is removed. Mr Gill recognises that Parliament may prior to actual withdrawal put in place a statutory protection mechanism; but that depends on the will of Parliament, which, he says, the Secretary of State cannot lawfully pre-empt. It is, he submits, a misuse of the prerogative to “foist” such a situation on Parliament; the rights to remain “must be addressed by Parliament before the giving of the article 50(2) notice.”
272. There are two problems with that submission. First, it is difficult to talk of the Executive “foisting” on Parliament a chain of events which flows directly from the result of the referendum which it authorised in the 2015 Act. Secondly, however desirable it would be for issues of detail such as those affecting his clients to be addressed at this stage, it is wholly inconsistent with the structure of article 50. That assumes the initiation of the process by a simple notice under article 50(2), to be followed by detailed negotiations leading if possible to an agreement on the terms of withdrawal. The details of the protections available for Mr Gill’s clients must depend, at least in part, on the outcome of those negotiations.
273. No doubt for this reason such an extreme argument is not adopted by the other respondents. They accept that, at this stage of the article 50 process, they cannot reasonably expect anything more than bare statutory authorisation for the service of the notice. That is realistic. But it also underlines the point that successful defence of the Divisional Court’s order will do nothing to resolve the many practical issues which will need to be addressed over the coming period, nor to protect the rights of those directly affected. Those problems, and the need for Parliament to address them, will remain precisely the same with or without statutory authorisation for the article 50 notice. If that is what the law requires, so be it. But some may regard it as an exercise in pure legal formalism.
274. Shortly after the 1972 Act came into force, Lord Denning famously spoke of the European Treaty as “like an incoming tide. It flows into the estuaries and up the rivers. It cannot be held back …” (Bulmer Ltd v Bollinger  Ch 401, 418F). That process is now to be reversed. Hydrologists may be able to suggest an appropriate analogy. On any view, the legal and practical challenges will be enormous. The respondents have done a great service in bringing these issues before the court at the beginning of the process. The very full debate in the courts has been supplemented by a vigorous and illuminating academic debate conducted on the web (particularly through the UK Constitutional Law Blog site). Unsurprisingly, given the unprecedented nature of the undertaking there are no easy answers. In the end, in respectful disagreement with the majority, I have reached the clear conclusion that the Divisional Court took too narrow a view of the constitutional principles at stake. The article 50 process must and will involve a partnership between Parliament and the Executive. But that does not mean that legislation is required simply to initiate it. Legislation will undoubtedly be required to implement withdrawal, but the process, including the form and timing of any legislation, can and should be determined by Parliament not by the courts. That involves no breach of the constitutional principles which have been entrenched in our law since the 17th century, and no threat to the fundamental principle of Parliamentary sovereignty.