A man who used his dual citizenship to buy military-grade firearms and ammunition legally in the US before selling them on to Irish criminal gangs has been jailed for 10 years.

Passing sentence on Conor O’Brien at the three-judge Special Criminal Court on Monday, Judge Karen O’Connor said criminal gangs need firearms to threaten and intimidate others and use them to maim, kill and terrorise.

She said O’Brien had shown a cavalier attitude towards the harm he was causing by playing a “crucial, if not imperative role” in providing arms and ammunition.

He took advantage of his dual citizenship to purchase guns in the US and sell them in the State for financial gain, she said, adding that the impact of such crimes “cannot be overestimated”.

In communications found on his phone, including one in which he joked about selling guns to “Ireland’s top criminals, LOL”, the judge said O’Brien had shown “total disregard for the impact of such deadly weapons on our citizens”.

While O’Brien’s guilty plea had been of value, she said the evidence against him was compelling as he had been caught “red-handed” with an extensive arsenal of firearms, ammunition and components in a shed he was renting.

The judge also noted that O’Brien had used his own name and details when purchasing the firearms and ammunition in the US, making them traceable to him and showing “an element of naivety” in what he was doing.

She cited as an aggravating factor the extensive planning and organisation involved in the importation and sale of guns as she set a headline sentence of 15 years, the maximum penalty available.

Having considered mitigating factors, including his guilty plea, she reduced the sentence to 11 years with the final 12 months suspended for one year. The court ordered the forfeiture and destruction of the firearms and ammunition. However, the court will hear further submissions next week regarding cash that was also seized by gardaí investigating O’Brien.

Counsel for O’Brien said there was no consent to the forfeiture of the cash in circumstances where money laundering charges that had been brought against him are no longer being pursued.

At a previous hearing, Det Insp Shane McCartan said: “Without Conor O’Brien, there would be no criminal organisation, such was his importance.”

O’Brien and the leader of the gun-running ring, Mark McCourt, were distributing guns and ammunition to criminal gangs in Derry, Armagh, Dublin and Limerick, he said.

Last November, O’Brien (29), of Kilpatrick, Ardee, Co Louth, was arraigned on six charges. He pleaded guilty that between February 10th, 2023, and July 19th, 2024, with knowledge of the existence of a criminal organisation, he did participate in or contribute to activity intending to facilitate the commission by the said criminal organisation or any of its members in the importation of firearms and ammunition and explosives.

He further pleaded guilty to five counts concerning the possession or control of a firearm or ammunition in suspicious circumstances. These related to offences at John Street, Blackstick, Ardee, on July 19th, 2024, when he had unlawfully in his possession two .233 Remington calibre barrels from AR-15 pattern semi-automatic rifles, in circumstances giving rise to a reasonable inference that he did not possess them for a lawful purpose.

He also had possession of four .233 Remington calibre barrels from Anderson manufacturing AM-15 pattern semi-automatic rifles; eight frames for Sig Sauer semi-automatic pistols; a frame for a Canik semi-automatic pistol; and four slides for a Sig Sauer model P320 9mm Luger calibre semi-automatic pistol.