A victims campaigner has been granted permission to mount separate legal challenges in Belfast and Dublin over the holding of a border poll.
Raymond McCord was already taking legal action over the British Government's alleged failure to implement a policy for going to the public on the constitutional issue.
Now, his solicitor says he has obtained leave from the High Court in Dublin to proceed with a case against the Irish administration.
With hearings due to take place in both jurisdictions next year, Mr McCord said, "I'm delighted, history is being created.
"This isn't about me, this is about removing the fear factor of a border poll being abused by politicians pitting one side against the other for political gain on the whole island of Ireland.
"The case against the Secretary of State for Northern Ireland questions the legality and transparency of current provisions for holding a border poll."
The 1998 Good Friday Agreement allowed for a referendum to be called if the Secretary of State believes a majority in Northern Ireland no longer wish to remain as part of the UK.
Mr McCord, a unionist who holds both British and Irish citizenship, insists he is not seeking a border poll.
But the Belfast man believes authority for calling such a significant ballot should not rest with one individual.
The campaigner has been an outspoken critic of loyalist paramilitaries since a UVF gang beat his son Raymond Jr to death in 1997.
He claims the existing criteria is too vague, undermines the Good Friday Agreement and could leave the decision open to political expediency.
Mr McCord has travelled to Dublin with his legal team to seek leave to mount a similar challenge against the Irish Government, Taoiseach, Minister for Foreign Affairs and Attorney General.
His lawyers argued that as a co-guarantor of the Good Friday Agreement, the Irish administration must also have a policy on the border poll issue.
Solicitor Ciaran O'Hare, of McIvor Farrell law firm, confirmed leave to continue with their case was granted.
"Given what has happened with Brexit, there's never been a more relevant time for this to be clarified," Mr O'Hare said.
"The court has accepted that there is a case to answer, and we can now proceed to a full hearing."
His client expressed delight at the outcome, but insisted the issue should have been resolved a long time ago.
"I'm not saying that I want a border poll, I just want clarity," Mr McCord added.