The conscription referendums of the First World War remain amongst the most divisive events in Australian political history. They sparked a number of libel actions, the most prominent of which was (in effect) between the leaders of the 'pro-' and 'anti-' conscription campaigns in the second referendum in December 1917: WM Hughes and TJ Ryan. The action, which resulted ultimately in an award of contemptuous damages to Ryan, reflected the limits of libel law, particularly in a jury trial, to deal satisfactorily with highly politicised issues such as conscription. Using archival and newspaper sources, this article argues that Ryan's faith in the legal and constitutional issues at the heart of his claim were misplaced given the doctrinal and forensic limits of the defamation action. Moreover, the conflict over the extent of federal power which lay at the heart of the political dispute gave the law of political libel in practice a field of operation with a distinctively Australian context.