On 1 January 1957 at the beginning of the IRA Border Campaign, he led the unsuccessful attack on Brookeborough Royal Ulster Constabulary barracks in which his associates Seán South and Fergal O'Hanlon, both the subjects of well-known republican ballads, were shot and fatally wounded.

He was arrested while trying to return to Dublin and sentenced in November 1959 to four years in Crumlin Road Gaol where he subsequently became officer commanding (O.C.)

[4][5] In the 1960s, Garland became a Marxist and was one of a generation of IRA leaders who attempted to lead the organisation away from violence and into left-wing political agitation.

[7][8] The US authorities announced that this scheme, which they said involved several international crime syndicates and transactions worth millions of dollars, had been uncovered in "Operation Mali".

[12] Copies of Kryuchkov's letter and of the Central Committee decision can be found in an archive of classified documents smuggled out of Russia by Vladimir Bukovsky.

On 7 October 2005, Garland was arrested in Belfast by British Special Air Service[13] following an extradition application issued by U.S. authorities.

[17] His supporters claimed the U.S. waited for Garland to travel north of the Irish border before seeking his extradition, believing the United Kingdom authorities would be more willing to acquiesce than those in the Republic of Ireland.

[18] On 9 October 2005, a Sunday Times article alleged that Garland became chief of staff of the largely inactive Official IRA in 1998.

[21] The campaign against his extradition continued, bringing in a number of prominent individuals from outside the Workers' Party including its Honorary Chairman Chris Hudson.

Garland also received support from the entertainment industry including musicians Pete Seeger, Christy Moore, Alabama 3 and John Spillane.

Garland spoke on his friend's passion, humanity, and quest for knowledge before handing Jake and Noel's daughter Ríona a starry plough, and an Irish flag.

[28][30] Then-party President Michael Donnelly, former leader Tom French, and Dublin City Councillor Mannix Flynn were in attendance at the funeral.