DISSIDENT republican party Saoradh is pursuing legal action against Facebook.
The group, which was founded in 2016, has accused the social media giant of political discrimination amid claims it removed pages from its platform.
Facebook said it cannot comment "as this is a legal matter" but confirmed it had received a letter of complaint from lawyers acting for the party.
Solicitors are seeking a court order to force the company to re-instate pages.
Their letter claims the decision to remove material was taken "due to our client's particular political view".
It is alleged this is a breach of the right to freedom of expression in Article 10 of the European Convention on Human Rights.
Solicitor Darragh Mackin told the BBC: "Our clients have no alternative but to seek injunctive relief to compel Facebook to uphold what is a very, very basic principle, the right to a political opinion and the right to expression."
Saoradh is supported by prisoners from the group known as the 'IRA' or 'New IRA' in Maghaberry and Portlaoise prisons
The Irish Republican Socialist Party (IRSP) has previously also complained after Facebook pages were shut down by the social media giant.
