A legal action has been launched by a British lawyer in Ireland to stop Britain from going through with Brexit.
Jolyon Maugham said he was seeking clarity from the ECJ on whether the UK could reverse Article 50 in future if a government were to decide that leaving would not, after all, be in its best interests.
Article 50 is the formal procedure for leaving the EU which Prime Minister Theresa May has promised to invoke by the end of March at the latest.
On Friday Maugham petitioned the High Court in Dublin to hear his case later this month, after raising more than £70,000 (80,000 euros, $85,000) through the crowdfunding website Crowdjustice.
"Can the United Kingdom just decide that leaving is a bad idea and pull the Article 50 notification?" Maugham said on RTE, Ireland's national broadcaster.
He is asking for clarification on the Article 50 process, noting that while it has yet to formally begin, EU member states -- including Ireland -- are acting as if it has by excluding Britain from EU summits.
"The plaintiffs will seek clarification of what rights as EU citizens will be lost (by triggering Article 50 will the UK automatically also leave the single market?)," he wrote in a press release.
They would also question "whether it is certain that their rights as European citizens will be lost (can Article 50 unilaterally be revoked by the UK?); and when they will lose their rights as European citizens (might Article 50 already have been triggered)."
Maugham said the case could have been lodged in any of the 27 states but it made sense to choose Ireland because the legal systems were similar and there was a shared language.
Maugham said he was confident the court would agree to hear the case later this month.
He argued that if the ECJ refuses to rule in favour of a possible reversal, Britain would be forced to accept whatever deal the EU foists upon it.