Paul Golding, 35, was arrested in Belfast, Northern Ireland, on Thursday.
Police detained him as they approached ground floor elevators and took him for questioning.
The arrest happened earlier this morning outside Laganside Court in the city.
The PSNI said: "Detectives investigating an incident at a peace wall in Belfast on Wednesday 14 December have arrested a 31-year-old woman in the Belfast area today".
Paul Golding, 35, was detained after accompanying his deputy, Jayda Fransen, to a court appearance in Belfast, where she faces charges of "using threatening, abusive, insulting words or behaviour" at the same rally, the Guardian reports.
First's Jayda Fransen today arrived at court to face public order charges over an "anti-terror" demo in Belfast.More news: Disney to buy Fox film, TV businesses for $52 billion
The deputy leader of the far-right Britain First group has been re-arrested in Belfast.
Prosecutors said footage and transcripts of Ms Fransen's speech "constitute the offences", arguing for restrictions to prevent her speaking at further rallies. "I can indicate there will be not guilty pleas to both charges", he said.
Fransen recently shot to global attention after US President Donald Trump retweeted three Islamophobic videos from her page to his 44.6 million followers. During the video post she criticised Islam.
A detective constable told the court police were seeking a further condition regarding the defendant's use of social media and the likelihood of reoffending.
The court ordered her not to go within 500m of any demonstration or parade in Northern Ireland as part of her release on bail.
She was allegedly involved in a video recorded outside Belfast's Islamic Centre which referred to it as a "den of iniquity".