EU court hears case on Brexit reversal raising fresh concerns for PM May

Lawyers acting for a group of Scottish politicians argued before the top European court Tuesday that the British parliament should have the power to unilaterally halt the countdown to Brexit.

A Scottish court has referred the case, which hinges on whether Westminster MPs could simply revoke Britain's "Article 50" EU withdrawal process, to the European Court of Justice.

Prime Minister Theresa May's British government argues it has no intention of halting Brexit anyway and that the case has been brought as a political tactic by pro-European opponents.

"Once Pandora's box is open, it's always difficult to close it," warned lawyer Lord Keen of Elie, urging the ECJ to throw out the case and "show respect for the UK parliament and the position of UK Government".

May is trying to sell an agreement on a "smooth and orderly" Brexit to a hostile House of Commons, arguing that their choice is to back a deal or face the economic calamity of crashing out of Europe without a plan.

But pro-Europeans hope that if the European court confirms that Britain has the right to stop the countdown then a third option would emerge: stopping Brexit altogether and remaining in the EU.

"It is fundamental to the treaties -- and to the values of the European Union -- that a member state can choose to revoke its withdrawal from the Union without the need for the unanimous agreement of all the other member states," argued lawyer Aidan O'Neill.

The European Union institutions also oppose the Scottish case, fearing member states will be tempted to launch their own speculative exit bids to extract concessions from Brussels -- only to reverse course.

"Can you imagine the state of uncertainty the process would put us in?" argued Karen Banks, a lawyer and senior European Commission official. "There would be chaos, uncertainty."

Under Article 50 of the Lisbon EU treaty, any member state can declare its intention to quit the union, a decision which for Britain comes into effect on March 29 next year.

Britain invoked the article on March 29, 2017 -- after voters backed Brexit in a national referendum the year before -- and is on course to formally leave EU institutions in less than five months.

The decision remains hugely controversial, however, and a group of politicians -- members of the Scottish, UK and EU parliaments -- has brought a case arguing that Britain should have the right change its mind.

But EU legal experts argue that all 27 remaining member states would have to agree to suspend the Article 50 process once it is launched.

The European Parliament has investigated the clause in the treaty and concluded, as did the Scottish courts that took up the legal challenge, that only the ECJ can make a legal ruling on the matter.

After Tuesday's hearing, the court retired to consider the arguments. The ECJ is treating the case under an expedited procedure but no date has been given for a ruling.

A court source told AFP that the decision could well be made before the end of the year, but the judges must first decide if the ECJ even accepts jurisdiction in the case.

(With inputs from agencies.)