The ECJ has been asked to deliver a preliminary ruling on whether Britain’s decision to leave the European Union can be reversed by Britain alone.
A source close to the case told Reuters, the ECJ hopes to make a decision before Christmas.
Theresa May’s Government is in talks with EU chief negotiator Michel Barnier and is hoping to thrash out a Brexit deal by March 29, 2019 with a major summit on the agreement due to take place later this month.
But Scottish lawmakers opposed to leaving the EU filed a petition to Scotland’s highest court, the Court of Session, in a bid to show the UK has the option of staying in the bloc once the outcome of Brexit is known.
The petitioners argue while there is no legal doubt that Britain could stop Brexit with the permission of the other 27 EU member states, the UK should seek to establish a legal right to do so unilaterally, whether the rest of the bloc likes it or not.
Lawmakers behind the challenge represent electoral areas in Scotland which voted strongly to remain in the EU in the June 2016 referendum.
The Scottish National Party, the strongest political party north of the border, has opposed leaving the bloc.
The Court of Session upheld the request and has asked the Luxembourg-based ECJ, which rules on the meaning of EU law, for a preliminary ruling.
We are giving it careful consideration,”
The British government, which has said it has no plans to reverse Brexit and therefore does not need to know, said it was disappointed by the decision.
A Government spokeswoman said: “We are giving it careful consideration.
“But as the Government has repeatedly said, we are committed to implementing the result of the referendum and will not be revoking Article 50.”
Jo Maugham, a lawyer who is funding the Scottish lawmakers, said: “This ship sailed yesterday – when the reference was sent to Luxembourg – and the Government wasn’t on it.”
“We believe it’s now too late.”
The Scottish petitioners argue legal certainty about the Brexit process is needed in advance of any British parliamentary vote on an EU withdrawal deal because no country has ever left the bloc before.
The Article 50 withdrawal clause in the EU’s Lisbon Treaty can be reversed with the permission of the other 27 EU members.
But the withdrawal clause does not specify whether the exit process can be unilaterally reversed.
Former British diplomat Lord Kerr, who drafted Article 50, has said Britain can change its mind at any stage before the final exit date in 2019.
A British Government spokeswoman did not immediately comment.