A man has been arrested in Co Cavan in connection with the murder of a UDR member in 1979.
The 67-year-old was detained on suspicion of murder, firearms offences and membership of a proscribed organisation by Gardaí on Monday.
The joint policing operation with the PSNI focuses on the murder of Joseph James Porter, who was shot dead outside his property in Mountnorris, near Markethill in Co Armagh on June 24, 1979.
The UDR man, who was in his sixties, was also a farmer, and his death was linked to the Provisional IRA.
The suspect was due to appear before a special sitting of the Extradition High Court in the Criminal Court of Justice on Monday.
His arrest was made under a Trade and Co-operation Agreement Warrant as part of the policing operation with the PSNI, whose Legacy Investigation Branch has been liaising closely with gardaí.