The case was brought before the court by several ‘concerned citizens’ who joined together at a hearing on 19 July when it was decided that the case brought by SCM co-founder Gina Miller would be the lead one.
The arguments centred on the question whether the government could lawfully use its prerogative powers to give notice to the European Union of its intention to leave or whether a vote in Parliament was required.
A government spokesperson confirmed to the BBC that the government would appeal the decision.
The landmark ruling is likely to delay any decision to leave the European Union and puts into doubt the timing announced by Prime Minister Theresa May, who had said she would trigger Article 50 by the end of March 2017.
It is unclear whether or not a quick vote could take place, or if MPs would first be expected to examine the complexities of the exit ahead of time.
Nigel Farage, former leader of the UKIP party said in reaction to the decision: “While constitutionally this may be correct because the referendum was legally advisory, I would think that in terms of political morality, parliament should want the will of the people to be carried out. I am becoming increasingly worried.”
In currency terms, the impact is perhaps slightly easier to predict. Martin Arnold, director, FX & Macro Strategist at ETF Securities said:“Today’s High Court judgement is likely to give fresh impetus to the Pound, as the ruling takes the decision about triggering Article 50 out of the government’s hand.
He added: “Optimism from investors is stemming from the fact that the UK Parliament will attempt to steer the UK further away from the ‘hard Brexit’ stance of the Conservative government, which will be less damaging for the UK economy.”