@Adeptus Arbitres are the police force of the Adeptus Terra, devoted to enforcing Imperial law throughout the entire Imperium. Utterly dedicated and without mercy, the Arbitres are feared throughout the galaxy, for they are the agents of a harsh law, where failure and incompetence are crimes, and the only punishment is death. Arbitres are empowered to act as judge, jury and executioner – citizens have no rights, and only members of the Priesthood of Terra or the Inquisition could claim anything so elaborate as a trial.
The Adeptus Arbitres enforce the Lex Imperialis, embodied within the great Book of Judgement. Their organisation represents the soldiers and police of the Adeptus Terra.[2] Each of the Imperium's worlds has its own government, laws, and its own local police forces to enforce those laws. The Arbitres concern themselves only with the enforcement of the broader laws to which the entire Imperium is subject; the common duty of the Arbitres is overseeing that the Governor of each world is regularly paying his planet's Tithe. In the event of a rogue Governor or a major revolt which threatens Imperial rule, the Arbitres will brutally intervene to restore order,[14b] killing or incarcerating entire noble bloodlines that were responsible for the events as well, if necessary. Following the removal of these individuals from authority the Arbitres then hold the power to place a specific tithe sanction upon a planet as an extra punitive measure.[28a][28b] In other circumstances, a planetary coup headed up by someone who will fulfil their duties to the Imperium will merely be observed, as a successful revolt by such a one just means that a weak ruler has been replaced