UK parliament must give Brexit approval, judges rule

"The government cannot trigger Article 50 without Parliament authorising that course," Lord Neuberger, president of the court said reading out the judgement.

This means May cannot begin talks with her EU counterparts about leaving the bloc until lawmakers give their backing.

MPs are unlikely to stop the process, although the judgment paves the way for closer parliamentary scrutiny of the negotiations.

The judges ruled that withdrawing from the EU makes fundamental changes to the UK's constitutional arrangements and removes some existing domestic rights of UK residents, therefore it requires parliamentary legislation.

"The change in the law required to implement the referendum’s outcome must be made in the only way permitted by the UK constitution, namely by legislation," the court said in the ruling.

Lord Neuberger also added that the judgment is not about leaving the EU or staying in, but about the right of the government to trigger the exit procedure.

Jeremy Wright, the attorney general, said the government was "disappointed" with the decision but would comply with it.

Downing Street confirmed that the government would trigger Article 50 by the end of March as planned.

Gina Miller, an investment manager who launched the case last year, said the victory was about the process and not politics.

"Only parliament can grant right to the British people and only parliament can take them away. No prime minister, no government, can expect to be unanswerable or unchallenged. Parliament alone is sovereign," she said.

Miller added that Brexit was "the most divisive issue of a generation", and she was shocked by the level of personal abuse she had received over the last months.

She said she hoped people in powerful positions will be "much quicker in condemning those who cross the lines of common decency and mutual respect".

Political consequences

The high court's ruling last year caused a massive backlash among Brexit supporters, with the Daily Mail newspaper condemning the judges as "enemies of the people".

The response is expected to be more muted this time, as the majority of MPs are expected to go ahead with triggering Brexit.

Opposition Labour leader Jeremy Corbyn said his party would not veto triggering Article 50, although some Labour MPs might defy him.

Corbyn said after the ruling that Labour would seek to amend the Article 50 bill to prevent Britain being turned into a tax haven and to defend social and environmental rules.

The Liberal Democrats and Scottish National Party are expected to put up resistance.

No veto for the others

The court ruled also ruled that the Scottish Parliament and Welsh and Northern Ireland assemblies did not have the right to veto triggering Brexit.

The judges argued that "relations with the EU and other foreign affairs matters are reserved to UK government and parliament, not to the devolved institutions".

This did not go down well in Scotland.

Prime minister Nicola Sturgeon has previously said she would propose an independence referendum if Scotland – which voted in favour of remain last year – is dragged out of the EU against its interests.

After Tuesday's ruling, Sturgeon said: "Although the court has concluded that the UK government is not legally obliged to consult the devolved administrations, there remains a clear political obligation to do so."