A High Court judgment that only parliament has the constitutional right to trigger the UK’s departure from the European Union has jeopardised plans set out by prime minister Theresa May barely a month ago, according to the Institute for Government.
Earlier today a panel of three judges backed a legal challenge to the government’s plans to use the Crown prerogative to enact the “leave” decision delivered in June’s referendum in a move welcomed by constitutional commentators but derided by leading Brexit figures.
The judges roundly dismissed arguments by secretary of state for exiting the European Union David Davis in favour of the government’s right not to involve parliament in triggering Article 50 of the Lisbon Treaty, the formal process for leaving the union.
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Davis contended that the when MPs agreed the European Communities Act 1972 – which gave effect to European law and rights in the UK – parliament had not intended to limit the Crown’s prerogative powers.
But judges said the act “clearly does not” give the Crown powers to use its prerogative to undo EU rights.
“It is clear that parliament intended to legislate by that Act so as to introduce EU law into domestic law in such a way that this could not be undone by exercise of Crown prerogative power,” they said.
They added: “The fact that parliament’s approval is required to give even an ancillary treaty made by exercise of the Crown’s prerogative effect in domestic law is strongly indicative of a converse intention that the Crown should not be able, by exercise of its prerogative powers, to make far more profound changes in domestic law by unmaking all the EU rights set out in or arising by virtue of the principal EU treaties.”
An official government response said the High Court decision would be challenged at the Supreme Court. A hearing date is set for December 7.
The IfG said today’s decision cast doubt on the schedule for effecting the UK’s departure from the EU, set out by May last month.
The prime minister said she would start the formal process of leaving the EU by the end of March, resulting in a departure by the end of 2019.
But the think tank warned: “[The government’s] loss in the High Court today will greatly impact proposed timeline for triggering Article 50.”
IfG director of research Hannah White said the judgement “placed a new obstacle on the road” towards the UK leaving the EU and meant Article 50 could currently not be triggered without parliament’s consent, most likely via a bill.
Dr White said she expected the Supreme Court would at least try to issue its judgement on the government’s proposed appeal before Christmas. But she cautioned that only a narrow window would remain for parliament to approve the triggering of Article 50 by the end of March if the High Court’s decision was upheld.
“If the prime minister wants to stick to her self-imposed March 2017 deadline, this new bill will have to be introduced as soon as possible,” she said.
“Given the government has only a slim majority in the House of Commons and no majority in the House of Lords, the time it will take for the bill to pass is uncertain.
"Depending on how the bill is drafted – and it is likely to be very short – there may be moves to amend it to place conditions on the Government before it can trigger Article 50.
"These could take the form of timing or process requirements – for example, a requirement on the Government to provide parliament with information about its negotiating position before triggering Article 50.”
Law Society president Robert Bourns meanwhile said the High Court decision gave the nation an opportunity to get constitutional clarity on use of the Crown prerogative.
“Article 50 explicitly says that notice of intention to withdraw must be given in line with the relevant member state’s constitutional processes,” he said.
“The ability to have such questions determined by an independent judiciary is central to the rule of law.
“Most commentators assumed that this case – whatever the outcome in the High Court – would be appealed to the Supreme Court so today’s ruling is a step along the road to a final decision."
The prime minister’s official spokeswoman told reporters that the High Court ruling would not stop preparations for the triggering of Article 50, and insisted it was still possible for the clause to be invoked before the end of March
“Our plan remains the same,” she said. “The British people voted. The government and the prime minister are going to deliver on the decision of the British people.”