Apparently it’s “in relation to an illegal parade” in Lurgan on 23 January this year.
Josephine Hayden from RSF said the government has failed on promises to phase out strip-searching at jails.
“There was a march planned for tonight to highlight the condition of prisoners in Maghabbery and Des was coming to speak at that,” Ms Hayden told UTV.
“The RUC pulled us in on Banbridge Street and arrested him because they said he attended an illegal march here in January. They need to leave him alone.
“There was an agreement to phase out strip searches, but they’ve completely and utterly reneged on that, absolutely and completely.”
Ms Hayden said the arrest is not linked to violence that has erupted close to the police station on Wednesday evening.
But, evidently, there are illegal parades, and then there are illegal parades…
Update From today’s BBC report
The president and vice president of Republican Sinn Fein have appeared in Craigavon Magistrates Court accused of organising an illegal parade.
Des Dalton, from Atheny, County Kildare, and Fergal Moore from Monaghan, are charged with arranging and taking part in the parade.
The march was organised in support of republican prisoner Martin Corry in Lurgan in January.
Both the men were released on bail to appear again in September