On 3 November 2016, the English High Court handed down its ruling in R (Miller) v. Secretary of State for Exiting the EU (Miller) in which it firmly rejected the UK Government’s argument that the Prime Minister could invoke Article (“Art.”) 50 of the Treaty on European Union (the “TEU”) without the prior authorisation of Parliament.
The implication of the judgment is that legislation will be required to trigger Art. 50. The Government had intended to give notice under Art. 50 by the end of March 2017. It has announced its intention to appeal the ruling to the UK Supreme Court, which is expected to hear the case between 5 and 8 December in an unprecedented full sitting.
The three judges who handed down the judgment have been the target of scathing criticism from certain quarters with some pro-Brexit sections of the UK media branding them “enemies of the people”. These unprecedented attacks on the judiciary, which have themselves been subject to condemnation in some quarters, underline how divisive the question of a Brexit has become. It is important to bear in mind three factors. First, the judgment was given by an unusually (for the High Court) senior group of judges; the Lord Chief Justice, the Master of the Rolls and a Lord Justice, giving the bench a similar profile to a Court of Appeal bench. Second, the judges were declaring the law based on centuries-old principles, not making new law. Third, their judgment stated that the government was in error at a basic level.
We examine below the legal questions, the arguments and the Court’s decision. We will then consider a number of possible outcomes.
The Question before the High Court
The sole question for the High Court in the Miller case was whether, as a matter of UK constitutional law, the Government, acting through the Prime Minister, is entitled to use Crown prerogative powers to trigger Art. 50 of the TEU, or whether the principle of Parliamentary sovereignty means that it can only be authorised by Parliament as a whole.
The Principles of Parliamentary Sovereignty and Crown Prerogative
The most fundamental rule of the UK constitution is that Parliament is sovereign and can make and unmake any law it chooses. Only Parliament can amend or repeal statutes. This includes the legislation that facilitated the entry of the United Kingdom into the European Community (now the EU), the European Communities Act (1972) (as amended) (the “ECA 1972”).
According to the High Court in Miller, the Crown’s prerogative powers constitute “the residue of legal authority left in the hands of the Crown”. The exercise of these powers is subject to constitutional limitations. Accordingly, Crown prerogative cannot be exercised to displace primary legislation and the Crown has only those prerogative powers that are recognised by the common law. However, and as a general principle, the Crown does have prerogative to conduct international relations on behalf of the UK, including in respect of the making and unmaking of international treaties on behalf of the UK.
The High Court in Miller explicitly acknowledged the “subordination” of the Crown or executive Government to law. Citing it as the “foundation of the rule of law” in the United Kingdom, the Court traced the origin of this principle to the early seventeenth century. The Court cited the Case of Proclamations of 1610 (Sir Edward Coke):
"the King by his proclamation or other ways cannot change any part of the common law, or statute law, or the customs of the realm" and "the King hath no prerogative, but that which the law of the land allows him."
Accordingly, the High Court accepted that it is a settled feature of UK constitutional law that Crown prerogative cannot be invoked to alter UK law or confer or remove rights of individuals under domestic law without the intervention of Parliament.
The Arguments of the Parties
The UK Government’s argument
The Government argued that, as the conduct of international relations falls within the prerogative powers of the Crown, the Government itself can effect UK withdrawal from the EU by giving notice under Art. 50 TEU. It further argued that, as such power could only be removed by primary legislation using express words to that effect, neither the ECA 1972 nor any other act of Parliament abrogated this aspect of Crown prerogative as they are silent on the issue. According to the Government, therefore, Parliament intended there to be a continuing “condition” for any EU rights to be given effect in domestic law in the shape of the UK’s continuing membership of the EU, and that such “condition” depended entirely on the conduct of international relations by the Crown.
The complainants' argument
Section 2(1) of the ECA 1972 provides that all “rights, powers, liabilities, obligations and restrictions” arising under the EU Treaties, together with all “remedies and procedures” that are to be given legal effect in the UK, must be “recognised and available in law and be enforced, allowed and followed accordingly”. In short, Section 2(1) provides that all directly applicable EU law is made part of UK law and is enforceable as such.
The complainants argued that the ECA 1972 therefore leaves no room for a Crown prerogative power to invoke Article 50 TEU. This is because the 1972 Act allows for the accrual of rights under domestic law by incorporating EU law into UK law. The government could not exercise the claimed powers without express authority. Any other interpretation would conflict with the fundamental principle that only Parliament can take away rights conferred by statute.
The Court’s Decision
The High Court firmly rejected the Government’s argument and declared that Art. 50 could only be invoked with the authorisation of the UK Parliament.
The High Court held that that the Government’s argument was contrary to the more fundamental constitutional principle of Parliamentary sovereignty. In this regard, the Court specifically stated that the “wide and profound” extent of the legal changes in domestic law created by the ECA 1972 made it “especially unlikely” that Parliament intended to leave the continued existence of such rights in the hands of the Crown through the exercise of its prerogative powers. The High Court also found that there was nothing in the ECA 1972 to support the contention that Parliament intended that the Crown would retain its prerogative power to effect a withdrawal from the EU and, by implication, to choose whether EU law should continue to have effect in UK domestic law.
The Nature of an Art. 50 Notice
It is worth noting that the Court in Miller did not have to consider the nature of Art. 50 notice; i.e. whether it is revocable or irrevocable. This is because the Government did not dispute the contention of the complainants that Art. 50 notice is irrevocable. However, some commentators argue that this question cannot now be ignored by the Supreme Court in the same manner.
The High Court held that the effect of the giving of irrevocable notice under Article 50 on relevant rights is direct, despite the fact that the Art. 50 process would take a while to be "worked through". Whether or not the Supreme Court will be compelled to address this question will therefore depend on the extent to which the Supreme Court considers that the Art. 50 notice will by its nature potentially affect relevant rights. The nature of an Art. 50 notice is a contentious issue of EU law that has not yet been tested either before the national or EU courts. This question could, in itself, add an additional layer of controversy and complexity. There might be an argument that, if an Art. 50 notice is revocable, giving such a notice does not necessarily lead to loss of statutory rights (in UK law).
Interestingly, the House of Commons Library has published a briefing paper (on 14 November 2016) on questions of whether the Court of Justice of the EU ("the CJEU") may have a role concerning the invocation of Art. 50. The paper considers whether an Art. 50 notice could be withdrawn (and why this issue is relevant to the Miller case) and whether the Supreme Court may find it necessary to refer a question on the interpretation of Art. 50 to the CJEU for a preliminary ruling (under Article 267 of the Treaty on the Functioning of the EU).
Conclusion and Possible Outcomes
Unless the Supreme Court overturns the High Court’s decision in Miller, the UK Government will have to seek the approval of Parliament as a whole, possibly through new legislation, before invoking Article 50 TEU. This risks, at the least, delaying the Government’s timetable for triggering Art. 50 and, by implication, the timing of the UK’s ultimate withdrawal from the EU. A decision by the Supreme Court to uphold the High Court’s judgment in Miller could also give rise to a number of potentially unwelcome outcomes for the UK Government.
Whilst the House of Commons could now be expected to support the required new measures to reflect the referendum result, it is possible that the need for the consent of Parliament could lead to lengthy debate. This could significantly delay the timetable for invoking Art. 50. The House of Commons could also seek to amend draft enabling legislation introduced by the Government in an attempt to allow for greater Parliamentary scrutiny and control in the negotiation process itself that will follow the triggering of Art. 50. The likelihood or not of this happening will depend on how the Government chooses to legislate for triggering Art. 50 (i.e. whether that would be by bill or affirmatory resolution). This, however, is a separate question.
The position of the upper (unelected) chamber, the House of Lords, is less clear. National legislation does allow the elected chamber, the Commons, to override the Lords. However, this is a cumbersome process which requires (amongst others) the passing of the contested legislation twice by the House of Commons. Nonetheless, there is potential for the Lords to delay (as opposed to block) the invoking of Art. 50.
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This article is part of our Brexit series
 By reason of the limitations of Crown prerogative discussed above, the Crown could not have ratified UK accession to the European Communities unless Parliament enacted legislation (i.e. the ECA 1972). This is because only Parliament could create the necessary changes to give effect to EU law in UK domestic law.
 Paragraphs 82 – 94 and 97 – 104.