Anti-eviction activist Ben Gilroy is one of two individuals who claim they were defamed in a video posted on social media by a campaigner for the rights of children with autism.
Mr Gilroy and businessman Vincent Byrne of Ardgillan Close, Ardgillan Heights, Balrothery, Co Dublin have brought defamation proceedings against West Cork based mother-of-five Fiona O'Leary who they claim defamed them in a 13-minute YouTube video she posted on June 23 last.
Ms O'Leary, represented by barrister Patricia Sheehy Skeffington Bl, denies that the post contains any defamatory remarks about the two men.
Ms O'Leary, the court heard, campaigns against those advocating the use of a substance called Miracle Mineral Supplement, (MMS) which has been held out to be a cure for autism in children.
Ms O'Leary, who has acted as a witness for the authorities in prosecutions against those promoting the use of the substance, says MMS contains bleach and is harmful to anyone who consumes it.
In a pretrial motion before Mr Justice Senan Allen, Mr Gilroy seeks an injunction requiring Ms O'Leary to take down the alleged defamatory video, which he says wrongly links him to the use and promotion of MMS until the case has been determined.
Representing himself, Mr Gilroy of Riverview, Athlumney Abbey, Navan, Co Meath said Ms O'Leary allegedly described the use of MMS as a form of child abuse.
He said the "false allegations" have very serious implications for him and his good reputation.
He claims that the defendant named in the post as being involved with a group called the "sovereign movement" which she alleges is involved in the promotion and use of MMS as a cure for autism.
He told the court that he is not a member of any such movement, nor has he anything to do with MMS.
Ms O'Leary denies the video is defamatory and opposes the injunction application on grounds that it breaches right to freedom of expression and rejects all of Mr Gilroy's assertions.
The court heard that it is accepted Mr Gilroy did not engage in the use or promotion of MMS.
In September, Mr Justice Tony O'Connor directed that Ms O'Leary either take down the YouTube post at the centre of the dispute or insert either by a video clip or by text at the start of the video stating her acceptance that Mr Gilroy is not engaged in the use or promotion of MMS.
Ms O'Leary says she complied with that order by inserting the required text, however Mr Gilroy says the video can still be seen on certain devices without the text.
The hearing of the injunction application continues.