Secular arm, in ecclesiastical law, refers to the legal authority of the civil power, the State, or any lay authority, invoked by the Church to punish offenders in cases properly belonging to the jurisdiction of the Church. In the Middle Ages especially in Inquisition trials for heresy, or grave immorality, ecclesiastical courts delivered convicted clerical and lay offenders over to the secular arm to administer severe capital punishments. The phrase "relaxed to the secular arm" was used by the Spanish Inquistion to describe the handover of the condemned heretic.
The medieval Latin phrase 'brachium seculare' was translated first into late Middle English.
Introduced circa 1180–1250 at the time of the Albigensian Crusade, the church inquisitors delivered a Cathar heretic, or any heretic, to the secular arm, to be burnt at the stake. Under canon law church tribunals had no jurisdiction to impose penalties involving mutilation or death. Notably the contrary circumstance of appeal by individuals to the secular authorities to interfere with, or hinder, the process of ecclesiastical jurisdiction was until recently punished in the Roman Catholic Church by excommunication.
- The Oxford Dictionary of Phrase and Fable, Religion
- Encyclopedia of the Middle Ages p.260
- The Concise Oxford Dictionary of the Christian Church (3 ed.)p.532