We asked readers for their questions and received more than 1,100 responses within five hours. Below are some answers to our most frequently asked questions.
Does this mean that now we may not be allowed to leave the EU?
The court ruling does not mean the end of Brexit.
The case was about the government’s right to trigger the formal two-year process of leaving the EU without there being a vote in Parliament.
The government is going to appeal against the decision – but, as things stand, the ruling means MPs and Lords will have to give their go-ahead before Prime Minister Theresa May starts her negotiations on the UK’s exit from the European Union.
Theoretically, they could decide to not to give the go-ahead – but, in practice, that is seen as highly unlikely given that a majority of people who voted in the June referendum voted for the UK to leave the EU.
What was the legal basis that swayed the decision?
Legal affairs commentator Joshua Rozenberg said the decision had been based on the argument the government could not use its executive powers because it would mean effectively overturning an act of Parliament.
Triggering Article 50 would eventually lead to the UK leaving the EU, which effectively takes away rights granted by Parliament, such as the right to free movement in Europe.
The High Court ruling effectively defined the limits of government power by reiterating that Parliament is sovereign – it can create laws and only Parliament can take them away.
What legal argument will the government use next month?
We do not know yet, but it may try to repeat the argument its prerogative powers allow it to trigger Article 50 because that in itself does not mean an immediate change to UK citizens’ EU rights.
What is the legal situation on whether Parliament needs to pass a legislative act in order to trigger Article 50 as distinct from just taking a vote?
Paragraph 13 of the ruling essentially states that a parliamentary motion is not enough to satisfy the terms of Brexit.
UK membership is bound not in prerogative power, but in the 1972 EU Communities Act and therefore needs primary legislation to be taken away.
Brexit Secretary David Davis said: "The judges have laid out what we can’t do and not exactly what we can do, but we are presuming it requires an act of Parliament."
Was the referendum result mandatory or advisory?
The EU referendum was advisory – as was discussed in the court ruling on Thursday.
It points to the "basic constitutional principles of parliamentary sovereignty and representative parliamentary democracy" in the UK, which "lead to the conclusion that a referendum on any topic can only be advisory for the lawmakers in Parliament unless very clear language to the contrary is used in the referendum legislation in question".
"No such language is used in the 2015 Referendum Act," it adds.
Could the case end up being decided at the European Court of Justice?
Possibly, but it would be surprising if it was, according to Joshua Rozenberg, because the case is about the UK’s constitutional requirements, not EU law.
Who made the submission to the High Court?
The lead claimant in the case is investment manager and philanthropist Gina Miller, who launched the case alongside London-based Spanish hairdresser Deir Dos Santos and a group called the People’s Challenge Group, which is backed by a crowd-funding campaign. You can read more about Ms Miller here.
Why does Article 50 need to be triggered at all?
Article 50 of the Lisbon Treaty is usually considered to be the only legal way to leave the EU. It states that a country which decides to leave the EU has two years to negotiate "arrangements for its withdrawal, taking account of the framework for its future relationship with the union". This will involve unravelling UK-EU treaty obligations; such as contributions to EU budgets, and holding talks on future trade relations. However some have suggested that the UK could leave the EU by other means – by amending EU treaties or repealing UK legislation. Douglas Carswell, then a Conservative MP – now UKIP – tried to introduce a European Communities Act 1972 Repeal Bill in 2012.
What questions do you have about the Article 50 High Court ruling?