This book considers the use made by Irish Republicans of British courts in the struggle for independence, over the period between the Easter Rising and the Civil War. It examines the complex relationship between the Republican movement and the British legal order: Republican ideology demanded a boycott of British legal institutions in Ireland and committed Republicans to refuse to recognize the authority of British courts. The Republican movement established its own rival court structure - yet Republicans were simultaneously able to make effective use of British courts to promote a separatist agenda. This book offers new insight, from original sources, into Sinn F in's most celebrated use of British courts - the challenges to death sentences imposed by martial law courts in 1921 - as well as lesser-known aspects of Sinn F in's legal strategy: the use of coroner's inquests and claims for compensation; legal challenges in the English courts to the policy of court-martial and internment; and the co-ordinated defence of those captured in the course of the Republican military campaign in Britain in 1920-1.