The decision means that both the House of Commons and House of Lords will need to approve a law allowing the Government to start the EU exit process.
At the centre of the legal case was the question of whether the Government, or Parliament, had the legal authority to give effect to the referendum result. The decision was not about the referendum result itself, but was concerned with ensuring the correct process was followed to implement the result, in line with the UK’s constitutional arrangements, which are not contained in a single document.
By a majority of 8-3, the Court ruled that only Parliament could give Government the authority to trigger Article 50, the mechanism which gives effect to the referendum decision. The main reason, according to the Court, was that because joining the EU entitled UK citizens to certain legal rights, which were conferred by an Act of Parliament, such as the right to travel and live in any EU country, it is only Parliament who could give the Government permission to retract those rights by passing another law.
The draft law, named the European Union (Notification of Withdrawal) Bill, consists of just 137 words, about a third of the length of this article. The bill has completed the first stage in its passage through the House of Lords, with further discussion to follow next week, after being passed without amendments by the House of Commons on 8th February 2017. The Government intends that the bill will become law in time for Article 50 to be triggered by the end of March.
Once Article 50 is triggered, the UK will remain a member of the EU for approximately 2 years during the exit negotiations, which are expected to be completed in mid-2019. During this two year period Parliament will also consider a law that will determine what EU legislation is incorporated into domestic law once the former ceases to have effect in the UK.