 Carrigan became President of his local branch of the United Irish League in 1898 and later became a member of the Irish Republican Brotherhood and in 1905 he became the Chairman of Sinn Féin’s first ever Cumann in Scotland, the Éire Óg Craobh Cumann.Carrigan joined the Irish Volunteers in 1915 after the split from Redmonds National Volunteers.In January 1916, Carrigan and fellow IRB members from Glasgow travelled to Dublin along with members of Na Fianna and Cumann na mBan and formed the Scottish Division of the Irish Volunteers and were based at the home of Count Plunkett in Kimmage, County Dublin where they prepared for an insurrection against British Rule in Ireland.