Parliament must vote on whether the UK can start the process of leaving the EU, the High Court has ruled.
This means the government cannot trigger Article 50 of the Lisbon Treaty - beginning formal exit negotiations with the EU - on its own.
Theresa May says the referendum - and existing ministerial powers - mean MPs do not need to vote, but campaigners called this unconstitutional.
The government is appealing, with a further hearing expected next month.
Really excellent news. It is vital that the issue is brought before parliament before Article 50 is triggered. Sadly, our government intends to appeal.
It's really shocking to see Conservatives attacking the very concept of the rule of law and checks on executive power.