During the Italian occupation of Libya from 1911 to 1943, colonial judges faced the problem of having to adjudicate over matters related to Islamic law or customary practice that were entirely absent from Italian legal codes. Although they accepted the general principle according to which Italy would respect local customs and principles of Islamic law, the absence of a clear and written compendium of what ought to be considered the local custom or shari‘a made it impossible for the colonial courts to pass judgment on such matters that referred to principles or institutions linked to Islamic law or customary practice. This was especially problematic in matters related to criminal law and law of contracts, which were under the sole jurisdiction of the colonial tribunals. In order to overcome this shortcoming, from the very outset of the colonial enterprise Italian authorities established that the sentences of the Court of Appeals of Libya constituted a body of jurisprudence that had binding legal value whenever there was silence of the law. The underlying idea behind this procedural novelty was that the sentences of Libya’s Court of Appeals would be the most immediate way to start sketching a new legal framework that would take into account local realities that found no correspondence in the Italian legal codes. The idea that a court ruling could become a legal norm is not without its problems, since, unlike common law, the Italian positive law rejected the formal use of court verdicts as a legal precedent. The recourse to such a system attests to the large degree of improvisation in which the colonial courts of Tripoli operated in order to make up for the absence of appropriate laws necessary to rule on customary or Islamic law matters that the Italian legislators were confronting for the first time. In this paper I propose to analyze how Italian authorities in Libya went about using the sentences of the Court of Appeals to create legal precedents in matters related to principles of Islamic Law and customary practice. A general discussion of the topic will be followed by a close look at the jurisprudence of the Court of Appeals of Tripoli on four matters that illustrate how Italian authorities sought to harmonize Islamic and customary law with their own colonial legal order. These four topics are: the right of pre-emption (shuf‘a), blood money (diya), Muslim Treasury (bayt al-mal) and patronage (wala’).