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Supreme Court

Parliament must vote on whether the government can start the Brexit process, the Supreme Court has ruled.


Article 50 provides that if a member state decides to withdraw from the European Union ‘in accordance with its own constitutional requirements’, it should serve a notice of that intention, and that the treaties which govern the EU “shall cease to apply” to that member state within two years thereafter.

Following the referendum in June 2016, the Government proposed to use its prerogative powers to withdraw from the EU by serving a notice withdrawing the UK from the EU Treaties.

The main issue in this matter was whether such a notice could, under the UK’s constitutional arrangements, lawfully be given by Government ministers without prior authorisation by an Act of Parliament.

The UK’s constitutional requirements are a matter of domestic law which was agreed should be determined by UK judges. The issues in these proceedings had nothing to do with political issues such as the merits of the decision to withdraw, the timetable and terms of so doing, or the details of any future relationship between the UK and the EU.

The claimants submitted that, owing to the well-established rule that prerogative powers may not extend to acts which result in a change to UK domestic law which withdrawal from the EU Treaties unquestionably would, the Government could not serve a notice unless first authorised to do so by an Act of Parliament. Resolution of the dispute depended on the interpretation of the European Communities Act 1972 (‘the ECA’), which gave domestic effect to the UK’s obligations under the then existing EU Treaties, together with subsequent statutes, which gave effect to and related to later EU Treaties, and the European Union Referendum Act 2015.

The High Court declared that the Government did not have power to give notice, without Parliament’s prior authority. The Government appealed to the Supreme Court against this decision.


The Supreme Court by a majority dismissed the appeal. The Supreme Court held that an Act of Parliament is required to authorise Government ministers to give notice of the decision of the UK to withdraw from the European Union.

Reading the summary, Supreme Court President Lord Neuberger said: “By a majority of eight to three, the supreme court rules that the Government cannot trigger Article 50 without an Act of Parliament authorising it to do so.

“Section 2 of the 1972 [European Communities] Act provides that, whenever EU institutions make new laws, those new laws become part of UK law. The 1972 act therefore makes EU law an independent source of UK law, until parliament decides otherwise.

“Therefore, when the UK withdraws from the EU treaties, a source of UK law will be cut off. Further, certain rights enjoyed by UK citizens will be changed. Therefore, the government cannot trigger article 50 without parliament authorising that course.”

The Supreme Court further ruled that there was no need for the Government to wait for consent from the devolved assemblies in Scotland, Northern Ireland and Wales.

Lord Neuberger stressed that the judgment is not about whether Brexit should happen, but rather the lawful process to authorise.

Reaction following the decision

A Downing Street spokesman said: “The British people voted to leave the EU, and the government will deliver on their verdict – triggering Article 50, as planned, by the end of March. Today’s ruling does nothing to change that.”

Gina Miller, one of the campaigners who brought the case against the government said Brexit was the “most divisive issue of a generation”, but added that her victory was “not about politics, but process”.

The Government remains committed to triggering Article 50 by 31 March 2017.

It is still not clear how the Government will proceed next, with the Supreme Court electing that it was not an issue for them to decide. It has been decided that the means to change the fabric of the UK rests with the UK Parliament alone. It is expected that ministers will shortly put forward a piece of legislation with the hope of getting MPs to approve it.

Supreme Court ruling – key points

  • The European Communities Act 1972 creates a process by which EU law becomes a source of UK law and so long as it remains in force, it means that EU law is an “independent and overriding source” of the UK’s legal system
  • Withdrawal from the EU makes a fundamental change to the UK’s constitutional arrangements because it will cut off the source of EU law and this fundamental change will be the inevitable effect of a notice being served
  •  UK constitutional requirements mean that such changes can only be made by Parliament
  • The fact that withdrawal from the EU would remove some existing domestic rights of UK residents also renders it impermissible for the government to withdraw from the EU Treaties without prior parliamentary authority

Do you want to understand the issues of the UK referendum result and work to minimise the effects it has on your business? DTM Legal outline practical steps you can take to manage the impact of Brexit on your business.

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