UPDATE 1-Can UK alone stop Brexit? Top EU court may decide before Christmas

The European Court of Justice (ECJ) has been asked for a preliminary ruling on whether Britain alone can reverse its decision to leave the European Union, according to a statement by Scotland's Court of Session on Thursday.

The ECJ hopes to make a decision on the case before Christmas, a source close to the case told Reuters.

Scottish lawmakers opposed to Brexit filed a petition to the Court of Session, Scotland's highest court, in August in an attempt to show that Britain has a unilateral option of staying in the world's biggest trading bloc, once the outcome of Brexit is known.

They argue that while there is no legal doubt that Britain could stop Brexit with the permission of the other 27 EU member states, it should seek to establish a legal right to do so unilaterally, whether the rest of the bloc likes it or not.

The lawmakers behind the challenge represent electoral areas in Scotland which voted strongly to remain in the EU in the June 2016 referendum. The United Kingdom as a whole voted to leave.

The Court of Session upheld their request and, less than two weeks later, has asked the Luxembourg-based ECJ, which rules on the meaning of EU law, for a preliminary ruling.

The Scottish petitioners argue that legal certainty about the process is needed in advance of any British parliamentary vote on an EU withdrawal deal because no country has ever before withdrawn from the European Union. (Reporting by Elisabeth O'Leary. Editing by Stephen Addison)

(With inputs from agencies.)