The European Court of Justice (ECJ) is due Monday to issue a decision on whether Britain could reverse its plan to leave the European Union, in a closely-watched case coming a day before British lawmakers vote on the Brexit deal.

Three outcomes are broadly possible: The court could decide that Britain can unilaterally halt the Brexit process; that other member states would have a say; or it could decide to reject the case after the British government argued that the question is hypothetical.

A top legal advisor to the ECJ recommended that Britain should be able to unilaterally reverse its decision, since it would be incompatible with EU rules to make this act of "sovereignty" dependent on the assent of all other member states.

The court usually follows the advice of its advocates general.

The petitioners, who initially brought the case before the Scottish courts, argue that lawmakers should be aware of all options when they cast their Brexit votes.

The case is being closely watched by those who favour a second referendum on Britain's departure from the EU. It has been handled under an expedited procedure due to the tight Brexit time frame.

The British parliament is due to vote Tuesday on the withdrawal agreement, a 585-page legal text detailing the terms of departure, as well as a political declaration outlining joint ambitions for the future relationship between Britain and the EU.

British Prime Minister Theresa May, whose Conservative Party is deeply divided on Brexit, has faced an uphill struggle to sell the deal to parliament.

Britain is due to leave the EU on March 29, 2019.