It is a case which has seen the Lord Chief Justice branded an 'Enemy of the People' by the UK media. As the Supreme Court retires to consider its decision, we examine the impact of 'Miller & Santos'[1] on the UK's withdrawal from the European Union.

Earlier this year, Gina Miller (an investment manager and philanthropist) and Deir Dos Santos (a London based hairdresser) launched a legal case against the Secretary of State for Exiting the European Union.

In essence, the Court was asked to decide whether, as a matter of constitutional law, the Crown – acting through the executive government – is entitled to use its prerogative powers (without the involvement of Parliament) to give notice under Article 50 of the TEU for the UK to cease to be a member of the EU.

At first instance

At first instance the case was heard by three eminent Judges including the Lord Chief Justice. They held that the Crown has no prerogative power to effect a withdrawal from the relevant EU treaties by giving notice under Article 50. This means that an Act of Parliament will need to be approved by the House of Commons and the House of Lords before the UK can give notice under Article 50.

Perhaps unusually, the UK does not have a codified constitution to be found in a single written document. Instead, it has established legal rules "…which govern the exercise of public power and which distribute decision-making authority between different entities in the state and define the extent of their respective powers." The rules regarding Crown prerogative powers are set out in cases dating back to the Case of Proclamations (1610) and in the Bill of Rights 1688.

The Judges at first instance primarily reached their conclusion due to the general constitutional principle that the Crown cannot change domestic law and nullify rights under domestic law unless Parliament has conferred upon the Crown the authority to do so, either expressly or by necessary implication by an Act of Parliament.

The European Communities Act 1972 (the 'Act') gives effect in each jurisdiction of the UK (England, Scotland, Wales and Northern Ireland) to binding obligations and rights arising under the EU Treaties. This implementing legislation was analysed in detail by the Court at first instance. The Judges concluded that in light of the constitutional background, it was clear that Parliament "…intended to legislate by that Act so as to introduce EU law into domestic law in such a way that this could not be un-done by exercise of Crown prerogative power."

In the Supreme Court

The government initiated a 'leap frog' appeal to the Supreme Court which was heard by all eleven permanent Supreme Court Judges earlier this month. They have retired to consider their Judgment which is expected in January.

The practical effect of the decision

Perhaps mindful of press criticism of the lower Court, in his closing remarks before the Supreme Court retired to consider its decision, Lord Neuberger said, "We are not being asked to overturn the result of the referendum. The ultimate question in this case concerns the process by which that result can be lawfully brought into effect."

If the government's appeal fails, it has said that it intends to introduce a short Act of Parliament to pass through the House of Commons and the Lords. The government expects that any delays to the "Brexit timetable" as a result would be minimal. It is also widely expected that the Act would be passed by Parliament, given that many MPs have openly stated that they would respect the result of the EU referendum.

Going through this parliamentary process, however, may well prompt opponents of Brexit or proponents of 'Brexit-lite' to seek to place conditions on how the government triggers Article 50. Many MPs are in favour of the UK remaining within the single market – if this was made a condition of leaving, then it could be that the UK is forced to accept other EU principles such as freedom of movement. These are issues which are continuing to cause sharp divisions in the UK.

We await the Supreme Court's ruling with interest…