It is often claimed that the constitutional history of the United Kingdom is the history of the tension between the Crown and Parliament. This historical narrative emphasises the ascendency of the latter institution over the former. It is an account of the British constitution which has found favour on the bench. For instance, in 1964, in R v Home Secretary ex p Fire Brigades Union Lord Browne-Wilkinson explains:

[T]he constitutional history of this country is the history of the prerogative powers of the Crown being made subject to the overriding powers of the democratically elected legislature as the sovereign body.

Given this historical context, it should come as little surprise that central to what was dubbed ‘the most significant constitutional law case in the UK for over a generation’ were questions about the relative powers of these two institutions. The case arose from the unique circumstances of giving effect to the UK’s withdrawal from the European Union. Indeed, the proceedings in R (Miller) v Secretary of State for Exiting the European Union were probably as close as it gets in the UK to the sort of constitutional adjudication which exists in jurisdictions with more easily ascertainable corpora of constitutional law like Australia. As the Supreme Court of the United Kingdom observes in Miller, unlike most liberal democracies, ‘the United Kingdom does not have a constitution in the sense of a single coherent code of fundamental law which prevails over all other sources of law.’

Beyond the core issue of the relative competences of the Crown and Parliament, the Miller litigation also brought together other disparate elements of the contemporary British constitution like no other case has done before. The case raised points on the ever evolving relationship between the UK Parliament and Government, and the devolved legislatures and administrations in Scotland, Wales and Northern Ireland. Also relevant to the litigation was the relationship between different sources of law. In particular, the mode through which obligations arising from international law are given effect in the legal systems within the UK. Notwithstanding the issue of justiciability being common ground between the parties, the case also raised questions about the institutional competence of courts themselves in dealing with ‘polycentric’ issues. As Lord Sumption has argued extra-judicially, when adjudicating over such multi-dimensional issues, ‘the relevant considerations will often be far wider than anything that a court can comprehend simply on the basis of argument between the parties before it.’

Given these multiple prisms through which to analyse the Miller judgment, this post focuses on one aspect of the appeal. It considers the place of the royal prerogative in the UK constitution in light of this seminal judgment. Concentrating on this element of the case may prove instructive to the discourse in Australia regarding the ‘nature and scope’ of the Commonwealth executive power in section 61 of the Constitution. As Isaacs J highlighted in the Wool Tops Case, in isolation, ‘the mere words of section 61 form an invariable measuring-rod of Commonwealth executive power.’ Section 61’s ambiguity raises the possibility of its nature and scope being determined in part with reference to the royal prerogative as canvassed by several Australian jurists (e.g. see Barwick CJ in Barton v Commonwealth and Brennan J in Davis v Commonwealth).

Furthermore, reflecting on the specific prerogative at issue in Miller may provide insight into whether treaty making powers should be subject to greater parliamentary control in Westminster systems of government. Joanna Harrington argues that a ‘democratic deficit’ may exist in these systems in this context. In Australia, this may require thinking about the adequacy of the scrutiny provided by the Commonwealth Parliament’s Joint Standing Committee on Treaties. While in the United Kingdom, the want of Parliamentary scrutiny over both ends of the Brexit process has already raised doubts about the democratic credentials of the current regime.

The core legal question in Miller

Article 50 of the Treaty on European Union (TEU) provides the framework through which a member state can withdraw from the EU. Firstly, it stipulates that any member state may withdraw from the EU ‘in accordance with its own constitutional requirements.’ Secondly, such a member state is required to give ‘notice’ to the European Council of that decision before negotiations leading to a ‘withdrawal agreement’ can begin. Thus, the question arose: From what constitutional source of authority could the UK Government notify the European Council of the decision to leave? Viewed independently from the political context of the referendum, at its most basic, this was a classic question of public law concerning the locus of legal authority for a particular governmental act. In this particular instance, whether the royal prerogative provided a sufficient legal basis for the Prime Minister to formally notify the European Council of the decision to leave the EU as asserted by the UK Government.

On petition for judicial review, a unanimous panel of a divisional court of the High Court of England and Wales dismissed the Government’s arguments, and held that the royal prerogative did not provide a legal basis for the executive to ‘trigger’ Article 50. On appeal, an 8 to 3 majority of the UK Supreme Court (sitting all available Justices) upheld the decision of the High Court. The Court expressly stipulated that only an Act of Parliament can provide the legal authority for the UK Government to formally notify the European Council of the decision to withdraw from the EU. What does this unequivocal judicial endorsement of statutory authority over the prerogative say about the prerogative’s place in the post-Miller world?

This ‘ancient and secret royal prerogative…’ what is it for?

When she appeared on the BBC’s Today Programme, the lead respondent in the appeal, Gina Miller, described the royal prerogative as ‘ancient and secretive.’ Similar characterisations of the prerogative were commonplace in parliamentary debates which took place after the referendum. However, as the Miller proceedings demonstrate, it is a misnomer to refer generally to ‘the royal prerogative.’ The ‘Governance of Britain’ green paper published in 2009 identified at least seven ‘main prerogative powers exercised by the Government’ in the 21st century. This included the power at issue in Miller – the prerogative to ‘make and ratify treaties.’ As unanimously affirmed by the Supreme Court, notwithstanding the centralisation of authority in legislature which followed the Glorious Revolution, ‘the Crown retained, as fully as ever, the prerogative of the treaty-making power.’

At the same time, the Court also notes that the number and scope of prerogatives has ‘progressively reduced as Parliamentary democracy and the rule of law developed.’ In this regard, Miller joins a line of authorities which characterise prerogative powers as ‘residual’ or ‘available’ in areas were the exercise of executive power is not underpinned by statute. As Tom Poole explains, the existing prerogatives are residual to the extent that their place in the constitution is dependent ‘on the sufferance from a sovereign Parliament.’ This is a view expressly endorsed by the Supreme Court. As the majority explains:

It is inherent in its residual nature that a prerogative power will be displaced in a field which becomes occupied by a corresponding power conferred or regulated by statute.

In terms of the specific prerogative to withdraw from treaties, the majority observes that it is itself a corollary of the power to enter into treaties. As the eight Justices assess:

There is little case law on the power to terminate or withdraw from treaties, but, as a matter of both logic and practical necessity, it must be part of the treaty-making prerogative.

In making this assessment, the Court leans on a speech by Lord Templeman in JH Rayner where the prerogative is described as including the constituent powers to ‘negotiate, conclude, construe, observe, breach, repudiate or terminate a treaty.’ The majority rejects descriptions of the relevant prerogative as ‘anomalous’ or ‘anachronistic.’ As their composite judgment explains:

There are important areas of governmental activity which, today as in the past, are essential to the effective operation of the state and which are not covered, or at least not completely covered by statute. Some of them, such as the conduct of diplomacy and war, are by their very nature at least normally best reserved to ministers just as much in modern times as in the past.

In his dissent, Lord Reed relies on a passage from Chapter 7 of Blackstone’s Commentaries to offer an even more targeted justification for the operation of different prerogatives in the broader field of foreign affairs. In the passage relied upon, Blackstone asserts that the conduct of foreign affairs:

… is wisely placed in a single hand by the British constitution, for the sake of unanimity, strength, and despatch. Were it placed in many hands, it would be subject to many wills: many wills, if disunited and drawing different ways, create weaknesses in a government; and to unite those several wills, and to reduce them to one, is a work of more time and delay than the exigencies of the state will afford.

On appeal, counsel for the Secretary of State emphasised more this Blackstonian, and perhaps ‘functional’ view of prerogative powers, more so than they did at first instance before the High Court. As the Secretary of State’s written case to the Supreme Court made clear:

It is, and always has been, for the Government to exercise those powers and to conduct the UK’s business on the international plane. The Government does so in exercise of the prerogative. That is a vital part of the conduct of modern inter-state business.

The assertion of a separate ‘international plane’ relates to the ‘dualist theory’ which underpins the relationship between municipal UK law and international law. The theory holds that, ‘the Queen acts throughout the making of a treaty and in relation to each and every of its stipulations in her sovereign character, and by her own authority’ (see Rustomjee v The Queen.) As such, agreements which come about from the exercise of this power are prima facie binding on the UK as a state, and do not confer rights or obligations enforceable in domestic courts. So, how were the rights and obligations arising from EU law, a form of international law, given effect over the course of the UK’s membership?

EU membership and the prerogative:

To give domestic effect to directly applicable EU law, before accession to the then European Communities, the UK Parliament enacted the European Communities Act (ECA) 1972. In one respect, the outcome in Miller turned on the status, and interpretation of this statute. In particular, section 2(1) of that Act which states:

All such rights, powers, liabilities, obligations and restrictions from time to time created or arising by or under the Treaties, and all such remedies and procedures from time to time provided for by or under the Treaties, as in accordance with the Treaties are without further enactment to be given legal effect or used in the United Kingdom shall be recognised and available in law, and be enforced, allowed and followed accordingly…

Through this provision, the 1972 Act not only gives effect to the relevant rights and obligations emanating from ‘the Treaties,’ but as the Court explains, ‘its effect is to constitute EU law [as] an independent and overriding source of domestic law.’ The latter point affirms the long-standing interpretation of section 2(4) of the ECA that, so long as the Act remains in force, EU law enjoys ‘supremacy’ over other sources of law. Uniquely, the ECA is said to ‘authorise a dynamic process by which, without further primary legislation, EU law not only becomes a source of UK law, but actually takes precedence over all domestic sources of UK law, including statutes.’ In fact, the majority emphasises the autonomous nature of EU law by asserting that the more ‘realistic analysis’ is that where EU law applies, ‘it is the EU [legislative] institutions which are the relevant source of that law.’ All this, according to the majority in Miller, is a function of the 1972 Act. Since the Article 50 notification will result in the abrogation of this statutorily sanctioned scheme, the Court concludes:

… that the royal prerogative to make and unmake treaties, which operates wholly on the international plane, cannot be exercised in relation to the EU Treaties, at least in the absence of domestic sanction in appropriate statutory form.

However, as contended by the Secretary of State and affirmed by the dissenting Justices, Ministers have on occasion effected variations in the content of applicable EU law over the course of the UK’s membership. Emphasising the employment of the phrase ‘from time to time’ in section 2(1), Lord Reed asserts that ‘Parliament has created a scheme under which domestic law tracks obligations of the UK at the international level, whatever they may be.’ This captures an argument advanced by John Finnis that the domestic operation of the ‘rights, powers and liabilities’ referred to in section 2(1) is ‘contingent’ on their availability in the EU Treaties as instruments of international law. According to Finnis, EU law rights:

[A]re non-statutory in the precise sense that Parliament has not enacted them, and in many, most or all cases has given them efficacy contingently on their coming into effect and remaining in effect ‘from time to time’ as treaty-based UK rights.

To this line of argument, the majority emphasises the difference between variations in the content of applicable EU law ‘from time to time,’ and the degree of change that will follow the Article 50 notification:

Withdrawal is fundamentally different from variations in the content of EU law arising from further EU treaties or legislation. A complete withdrawal represents a change which is different not just in degree but in kind from the abrogation of particular rights, duties or rules derived from EU law. It will constitute as significant a constitutional change as that which occurred when EU law was first incorporated in domestic law by the 1972 Act.

What is arguably novel here is the pre-emptive ousting of the prerogative from the indeterminate enterprise of effecting ‘significant’ constitutional change. As a matter of principle, the majority could not ‘accept that a major change to UK constitutional arrangements can be achieved by ministers alone.’ As they make clear, such a ‘far-reaching’ change can only be ‘effected in the only way that the UK constitution recognises, namely by Parliamentary legislation.’

The dissentients also emphasise the absence of express, or necessarily implied legislative intention to remove the prerogative in respect of withdrawing from the EU. On this point of interpretation, the dissenting Justices’ reasoning is closer to the approaches adopted in Canada and Australia. In Turp v Minister of Justice, the Federal Court of Canada held that an Act of Parliament implementing the Kyoto Protocol had not removed the prerogative to withdraw from that Agreement. Even though the Kyoto Protocol Implementation Act committed the Canadian executive to the obligations emanating from the Protocol, the Court found that it ‘did not expressly alter the royal prerogative [to withdraw] and that no provision or condition of the Act [did] so by necessary implication.’ This chimes with the view expressed by several Australian judges. In Barton, Barwick CJ made it clear that ‘the rule that the prerogative of the Crown is not displaced except by a clear and unambiguous provision is extremely strong.’ In the Tampa case, then French J advocated an even stricter, and contextual approach which gave weight to the specific power at issue. In his view:

The greater the significance of a particular executive power to national sovereignty, the less likely it is that, absent clear words or inescapable implication, the parliament would have intended to extinguish the power. In such a case, close scrutiny will be required of any contention that a statute, without express words to that effect, has displaced the operation of the executive power by virtue of ‘covering the field’ of the subject matter.

The reasoning and conclusion of the majority in Miller can be seen as a repudiation of this approach. Although treaty making is undoubtedly ‘a power significant to national sovereignty,’ the conclusion reached in Miller appears to rest on the sui generis nature of EU Treaties. As they emphasise, EU Treaties ‘not only concern the international relations of the United Kingdom […] they are a source of domestic legal rights many of which are inextricably linked with domestic law from other sources.’ Thus, the question in Miller was not one of finding evidence of an express or implied intention to displace a pre-existing power to withdraw from the EU. According to the majority, ‘the proper analysis is that, unless [Parliament] positively created such a power in relation to those Treaties, it does not exist in the first place.’

Taken as a whole, the majority judgment provides support for the normative observation made by Cheryl Saunders in 2015 that, ‘the heady combination of internationalisation and democratisation raises doubts about whether [treaty-making] is appropriate for exercise by the executive alone.’ Outside the evidently unique context of EU Treaties, in the UK, treaties have to be ‘laid before Parliament’ for a period of 21 days before ratification as required by section 20 of the Constitutional Reform and Governance Act 2010. The extent to which this scheme is an advancement on the work done by the Joint Standing Committee on Treaties in Australia is questionable. The 2010 Act merely puts the long-standing Ponsonby convention on a statutory footing, while in substance, maintaining executive control over the treaty making process.

Conclusion: The broader constitutional balance

The outcome in Miller lends support to the thesis that the UK constitution firmly embraces legal, as well as political constraints on public power. Within an over-arching framework of legislative supremacy, British courts have an essential role of ‘umpiring’ the relationship between the different arms of the state. This is mainly a function of the courts’ competence to provide answers on where the uncodified constitution vests authority for particular governmental acts. The UK Parliament has since enacted the EU (Notification of Withdrawal) Act 2017. Section 1 of the Act provides the Prime Minister with the requisite authority to notify the European Council as specified by the Court. This formal notification will be sent on March 29. At least in this very early stage of the Brexit process, there appears to be no place for the prerogative.

Byron Karemba is a PhD Student at the University of Leeds. He would like to thank Dr Gabrielle Appleby and Lynsey Blayden for comments on earlier drafts of this piece. The usual disclaimer applies.

Suggested citation:  Byron Karemba  ‘Locating the Place of the Royal Prerogative After Miller‘ on AUSPUBLAW  (22 March 2017) <>