Pim served in the Liberal administration of H. H. Asquith as Solicitor-General for Ireland from 1913 to 1914. The latter year he was sworn of the Irish Privy Council and promoted to Attorney-General for Ireland, a position he held until 1915, when he was appointed a justice of the Queen's Bench Division of the High Court of Justice in Ireland. After the Easter Rising of 1916 he was briefly appointed a Lord Justice of Ireland, charged with emergency powers of government.