This Kat sat in Court for two of the three days of the legal argument in the "Brexit Challenge" - a legal case in the High Court of England and Wales in which two groups of claimants, together with some interveners and interested parties, argued that the Government could not invoke Article 50 of the Treaty on European Union (which starts the procedure by which the UK would leave the EU) under so-called "Crown prerogative" powers, that is, ministerial power exercised without parliamentary authority. They argued that the prerogative cannot be used to take away rights granted by Act of Parliament. The Government countered that the entering and leaving of treaties is a prerogative act, and that there was no need to involve Parliament at the Art 50 notification stage, but that Parliament (probably, and almost certainly) would be involved in passing the necessary consequential national legislation. But as many observers pointed out, by then it would be too late for Parliament to make any real contribution, as once Article 50 is triggered, leaving the EU is inevitable - unless Article 50 is reversible, which the Government conceded for the purposes of this litigation that it is not. The Government also conceded that Art 50 notification cannot be given conditionally.
I doubted the Government position on the logical basis that while the Crown signs and ratifies an international treaty, if it has effect on domestic law then before ratification Parliament must pass the necessary legislation. If it does not, then ratification is impossible and does not occur. For the domestic law thus passed to be able to be frustrated by a ministerial act under Crown prerogative, to leave the treaty and therefore remove the effect on domestic law, seemed highly anomalous.
Today, the Decision has been handed down, and the two most senior judges in the Courts of England and Wales - the Lord Chief Justice Lord Thomas of Cwmgiedd, the Master of the Rolls Sir Terence Etherton, together with Lord Justice Sales (all judges in the Court of Appeal, but here sitting as High Court judges in the Divisional Court of the Queen's Bench Division) unanimously found against the Government.
The text of the Decision is here, and the summary prepared by the Court is here. The citation is R (Miller) v Secretary of State for Exiting the EU  EWHC 2768 (Admin). It is not long (111 paragraphs) and is great reading.
The judgment emphasises that the question is a legal question about how a decision to leave the EU can, in law, validly be taken and notified, NOT a political question about whether the UK should leave the EU or not.
The Court confirmed the common ground between the parties that "the most fundamental rule of UK constitutional law is that the Crown in Parliament is sovereign and that legislation enacted by the Crown with the consent of both Houses of Parliament is supreme" - i.e. Parliamentary sovereignty gives supreme legal authority to an Act of Parliament. The powers of the Crown prerogative, i.e. the power of the Crown to act without Parliament, are delineated by UK constitutional law. The Crown prerogative is the vestige of the powers of the monarch, but now exercised by ministers. The most famous expression of the limit of Crown prerogative is Sir Edward Coke in The Case of Proclamations:
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;
the King hath no prerogative, but that which the law of the land allows him.
This is also confirmed in the Bill of Rights 1688.
The Court found that although the making and unmaking of treaties is a Crown Prerogative act, this is precisely because a treaty cannot alter domestic law. Thus in making or unmaking a treaty, the Crown cannot without the intervention of Parliament confer rights on individuals or deprive individuals of rights.
The Court noted that the Crown could not have ratified the accession of the UK to the EC (European Communities as they then were) unless Parliament had enacted legislation. This was done by the European Communities Act 1972. The ECA 1972 through Section 2(1) thereof applies EU law ("rights, powers, liabilities, obligations and restrictions from time to time created or arising by or under the Treaties") to the UK. If the UK withdraws from the Treaties that govern the EU, then there will be no such EU rights to which this provision will have any application, so Section 2(1) will be stripped of any practical effect.
The Court accepted the claimants' arguments that EU rights such as the rights to free movement within the EU, which currently are enjoyed by UK citizens, even though they are formally not a product of UK law but of EU law in conjunction with that of the Member State to which the UK citizen is moving, and are not enforceable in national courts in the UK (as the Government argued), are nevertheless to be regarded as rights that Parliament intended to bring into effect, and did in fact bring into effect, by enacting the ECA 1972.
The Court rejected the whole basis of the Government's arguments, namely that the Crown prerogative remained to unmake a treaty unless there was clear statutory intent to remove it, as "flawed at this basic level". Instead the Court emphasised the basic constitutional principles that the Crown cannot use its prerogative powers to alter domestic law, and that the prerogative powers can only be exercised on the international plane. Thus, the Court concluded that:
The Crown therefore has no prerogative power to effect a withdrawal from the relevant Treaties by giving notice under Article 50 of the TEU.
In our judgment, the clear and necessary implication from these provisions taken separately and cumulatively is that Parliament intended EU rights to have effect in domestic law and that this effect should not be capable of being undone or overridden by action taken by the Crown in exercise of its prerogative powers. We therefore reject the Secretary of State's submission that Parliament did not intend to abrogate the Crown's prerogative powers and had not done so through the ECA 1972. Parliament also intended that British citizens should have the category (ii) rights [eg freedom of movement] and that, likewise, they should not be capable of being undone by the Crown in exercise of its prerogative powers. We arrive at this conclusion and reject the Secretary of State's submission by interpreting the ECA 1972 as a statute which introduces EU rights into domestic claw and must be taken to cover the field. The ECA 1972 cannot be regarded as silent on the question of what happens to EU rights in domestic law if the Crown seeks to take action on the international plane to undo them. Either the Act reserves power to the Crown to do that, including by giving notice under Article 50, or it does not. In our view, it clearly does not.
The Court reached basically the same conclusion following the claimants' main argument that the Crown cannot change domestic law and nullify rights under the law unless Parliament had conferred upon the Crown authority to do so either expressly or by necessary implication by an Act of Parliament. The Court considered that the ECA 1972 confers no such authority on the Crown.
So, finally the Court concluded:
For the reasons we have set out, we hold that the Secretary of State does not have power under the Crown's prerogative to give notice pursuant to Article 50 of the TEU for the United Kingdom to withdraw from the European Union.
So, absent any appeal, an Act of Parliament (ie passing through both the House of Commons and House of Lords) is needed to invoke Article 50. MPs will probably vote according to the referendum result, but may seek to influence the type of exit agreement from the EU to be sought. The House of Lords may not feel so constrained.
The Court has certified the case as one suitable for a "leapfrog" appeal to the Supreme Court, and the Supreme Court apparently has dates set aside on 7 and 8 December to hear the case, sitting as all 11 judges. But maybe the Government will not actually appeal, preferring instead to use the time to get the necessary Bill through Parliament. The next few weeks will be interesting.