The McBrearty family has criticised the Minister for Justice after he refused to meet them in Dublin today.
They said they would now pursue their case through the courts and in Europe if necessary, to ensure their legal costs at the Morris Tribunal are covered.
The meeting was cancelled after Michael McDowell claimed the family placed pre-conditions on the meeting.
The minister said the family declined to bring their legal representatives to the meeting, which was to discuss their concerns about the State's refusal to guarantee their legal costs.
Mr McDowell insisted he could not treat them differently to other witnesses and claims they had also wanted to bring other people to today's meeting who he had not agreed to meet.
Last month, Frank McBrearty Senior walked out of the tribunal because of the State's failure to guarantee the family's legal costs at the hearings.
The Government has consistently said it cannot give a guarantee on costs because it was solely an issue for the tribunal, which could only make such a decision when it had concluded its work.
The tribunal is examining allegations of garda corruption in Co Donegal that came to light after members of the McBrearty family were falsely accused of the murder of cattle dealer Richie Barron.