The Assizes of Ariano were a series of laws promulgated in the summer of 1140 at Ariano, near Benevento in the Mezzogiorno, by Roger II of Sicily. Having recently pacified the peninsula, constantly in revolt, he had decided to make a move to more centralised government. The assizes established the large Sicilian bureaucracy and sought to maintain the feudal system under strict royal control. It contained forty clauses that touched on all possible topics of contemporary legal concern: private property, public property, the church, civil law, royal finances, the military. The work was advanced for its day, deriving its precepts not only from Norman and French, but also Muslim and Byzantine (especially Justinian), legal theories.
The first half of 1140 was spent by Roger in Palermo preparing the assizes. They were certainly well-planned. Despite having written the legislation in his capital, in July, he traveled in state to Salerno, the capital of the duchy of Apulia, and thence to the Abruzzi, where he examined the conquests of his sons: Roger and Alfonso. These men, now duke of Apulia and prince of Capua respectively, had consolidated the peace on the peninsula and made it possible for the great legislation that year.
The assizes affirm that the king is the only lawgiver in Sicily, that he is both judge and priest (he held the legatine powers from the pope), and all Sicilians were equal and under the same laws, whether Latin, Greek, Jew, or Muslim, Norman, Lombard, or Arab. It punished treason with death. It was also detailed in other crimes of violence: cowardice in battle, arming a mob, or withholding support from the king or his allies. Ecclesiastically, Christian heretics and apostates lost their rights. Bishops were excused from attendance at courts, though the king was granted override on this, as on everything, and there could be no appeals. Militarily, the knightly class was closed. Nobody could become a knight if had no knightly lineage. Finally, the assizes did not ignore the commoners and demanded that they be treated with justice and be burdened not unduly by their lords.