On 28 February 1916, William Cairns applied for total exemption, stating: “I conscientiously object to all wars and the taking of human life which I hold to be sacred. The world is my country, mankind are my Brothers to do good is my religion.”
On 20 March he was granted exemption from combatant service only, but, following the appeal of a military representative, the appeal tribunal granted him exemption from combatant service only. William unsuccessfully appealed against this decision
He was assigned to the Non Combatant Corps on 14 March 1916 in Edinburgh. He was court-martialled in Hamilton on 22 June 1916 and sentenced to 112 days hard labour in Balinnie civil prison. He was imprisoned from 26 June 1916 to 5 October 1916 when he was released to the Home Office Scheme in Wigtown. On 1 November 1916, he was assigned to the Army Reserve Class W.