[1] McCristal became active in the local Wharf Labourers' Union, forming an association with Billy Hughes who remained its secretary while serving in federal parliament.
He enlisted in the Australian Imperial Force at the outbreak of World War I, serving in the 1st Light Horse Regiment.
McCristal remained active in the anti-conscription campaign, and in August 1917 he was arrested and charged with sedition following a meeting at the Sydney Domain, in which he called the King and parliamentarians "parasites".
During this period he was in court three times: once in 1922, when he was fined £10 for encouraging a strike; again in 1932, when he was acquitted of causing bodily harm after a conflict with a sub-tenant; and finally in 1933, when he unsuccessfully sued the Sun for libel regarding its account of the 1932 case.
He contested the 1943 federal election for the "Soldiers, Citizens and War Workers Labor Party" (sometimes spelt 'Labour'), running in the seat of West Sydney.
[1] McCristal attracted some attention in 1952 when he attended the funeral of his old foe Hughes, who he said had "contributed much to Labor's cause and been a great Australian".