The main sticking point is a "backstop" provision that aims to guarantee an open border between European Union member Ireland and the U.K.'s Northern Ireland after Brexit.
Monday's ruling is in line with an opinion delivered last week by a Court legal adviser.
"We don't want to stay in the European Union ... so this case is very well but it doesn't alter the referendum vote or the clear intention of the government that we leave on March 29", Gove told the BBC.
But even if she wins concessions from European leaders, which is not guaranteed, MPs will be able to table amendments on a fresh proposal, potentially forcing the government to alter its Brexit strategy once again.
The Northern Irish party which props up May's minority government bluntly told her to ditch the backstop altogether or face the collapse of her deal.
The ruling comes ahead of a Commons vote on Theresa May's Brexit deal on Tuesday.
The issue has been legally tricky because while Article 50 of the EU's Lisbon Treaty tells member states how to start the process of leaving the bloc, it offers no help on what to do it if they change their mind.
Motion Picture Academy was BLINDSIDED by Kevin Hart quitting over homophobic tweets
Reportedly among those who turned down the proposal to host the show are Oprah Winfrey, Jerry Seinfeld and Justin Timberlake. Hart stepped down as host in response to public outrage over years-old tweets that contained homophobic references.
The ECJ said it made the ruling to "clarify the options open to MPs" ahead of voting on Mrs May's deal.
Many lawmakers were scathing in their comments about both May's actions and the Brexit deal, and derisive laughter erupted when May claimed there was "broad support" for many aspects of the plan.
A government spokesperson said: "We note the judgment from the CJEU but this does not change the government's firm policy that we will not revoke Article 50". Anti-fascists and Labour party members were among those marching against Brexit.
The febrile political atmosphere was reinforced by rival rallies that drew thousands in different parts of London over the weekend.
A senior ECJ official - the advocate general - said last week he agreed the United Kingdom should be able to change its mind about leaving.
A minister in the devolved Scottish government, which backed the referral of the case to the ECJ, noted that most Scots had voted against Brexit. If she loses, her own position could be in jeopardy, there could be a move for a new election, or possibly to hold a new referendum.
In September, Centre for European Reform research claimed that Brexit was costing the United Kingdom economy an enormous £500 million a week. Boris Johnson, who was instrumental in the Leave campaign's victory, said that defeat for the Prime Minister would not necessarily cost May her job, but she would have to go back and renegotiate the terms of the deal.
Quelles sont les émissions en ligne les plus demandées par les utilisateurs?
Les disciplines sportives les plus populaires Les émissions sportives en direct sont de plus en plus accessibles. Récemment, les émissions sportives sont de plus en plus populaires sur Internet.
They sought a declarator from the Courts on whether, when and how the notification made by the Prime Minister under Article 50, which will lead to the UK's withdrawal from the European Union on 29 March 2019, can be unilaterally revoked.
The case was originally heard by the Court of Session in Edinburgh and two attempts by the UK Government to appeal against the referral to the European court were rejected.
The ECJ judges ruled this could be done without altering the terms of Britain's membership.
"We don't want to stay in the EU".
The government did not spell out the mechanism for delaying the vote scheduled for Tuesday.
British Prime Minister Theresa May on Monday began a final push to persuade parliament to back her Brexit deal as the European Court of Justice ruled Britain was free to halt withdrawal from the bloc unilaterally.
Stephen Curry Thinks the Moon Landing Was Faked
The world is flat", O'Neal said on a podcast previous year . "I do not go up and down at 360-degree angle, and all that stuff about gravity".