On Thursday 3 November, the High Court ruled against the Government and said that Parliament must vote on whether the UK begins the process of leaving the EU.

The High Court handed down its judgment in Miller (R) v Secretary of State for Exiting the European Union, the judicial review launched by a number of individuals challenging whether the Government alone can remove rights granted to them under the EU Treaties.

The question before the High Court was whether parliamentary approval is necessary before the Government can trigger Article 50 and begin Brexit negotiations with the EU. The case proceeded on the basis that notice under Article 50 can only be given unconditionally and once given cannot be revoked.

The Government argued that as a general principle, international treaties are within its prerogative and so it can issue the Article 50 notice without obtaining the consent of Parliament. It also argued that this right extended to withdrawing from EU treaties.

The High Court disagreed and distinguished European Union Treaties from other international treaties. It noted that EU law had been incorporated into domestic law by virtue of the European Communities Act (ECA) and that the Government cannot as a matter of principle overrule an Act of Parliament. The rights and obligations flowing from the ECA could not be undone by the exercise of the Royal Prerogative.

The Government has since announced that it will appeal the judgment of the High Court. The appeal will be heard before all Supreme Court judges in December, the parties having agreed to leap-frog the Appeal Court.

If the High Court's judgment is upheld, a key question will be what form Parliament's consent will take. Parliament is unlikely to give a blank cheque to allow the Government to negotiate Brexit as it sees fit. Parliament has already expressed a desire to have a role in the terms put forward for Brexit, for example as regards the extent to which the UK will continue to participate in the single market. Any parliamentary approval to trigger Article 50 may therefore be expected to be subject to various conditions designed to hold the Government to account. Tensions are therefore likely to arise between the Government's wish to not give a running commentary on its Brexit position and the right of Parliament to scrutinise the Government. Equally, once the Article 50 notification has been given, continued parliamentary scrutiny would appear certain if the reasoning of the High Court is upheld.