Published Wednesday, 12 February 2014
Andrew Allen, who was murdered in Buncrana two years ago. (© Pacemaker)
Mr Allen, 24, was shot dead on 9 February 2012 at Links View Park in Buncrana.
The father-of-two was originally from the Top of the Hill in the Waterside area of Londonderry, but was one of a number of people intimidated out of the city by dissident republican group Republican Action Against Drugs.
The arrested man was detained in Co Donegal under Section 30 of the Offences against the State Act, 1939 on Wednesday and was taken to Buncrana Garda Station.
A spokesperson from An Garda Síochána said: "Investigations are continuing."
There are no further details.
© UTV News