Recent scholarship on Islamic law tends to accord a positive value to custom. In Wael Hallaq’s compelling narrative, custom and customary law were the medium by which the universal principles of the Sharīʿa were localized and translated into the social order: “Having evolved over the millennia, and adapting to every political, dynastic and legal turn, these customs absorbed, and indeed influenced, the Sharia in multiple and particular ways, depending on the specific local context. Custom and customary law thus stood in a dialectical relationship with religious law, but never lost their independence from this law or, especially, from political intervention.”
Like Adam Smith’s Hidden Hand, custom appears to have evolved organically in response to the needs of local communities, ever independent of state control. But Hallaq is vague about the actual content of custom in pre-modern societies. He gives no definition, only a rather limited reference to local practice, ʿurf, in defining the meaning of legal categories.
It seems that “custom” is often used today as a shorthand for “community,” and I see much that is good in highlighting communities over states, societies over jurists. But as a social and legal historian, I am not convinced that such a view of customs and customary laws represents the realities of pre-modern Muslim societies.
First, there is a problem of definition, with different authors using the same term to mean quite different things. In its most restrictive definition, “custom” or ʿurf means the linguistic and social interpretations of a sharʿī term, for example, determining the value of a dirham in a given locality. This is in fact the meaning found most commonly in fiqh books.
At another level, ʿurf refers to widespread legal practices that have not been sanctioned by the early Islamic authorities, but are valorized by later jurists. Many of the examples of this type of custom are agricultural contracts, especially share-cropping, which are approved by medieval jurists even though they invariably involve risk. This type of ʿurf has been aptly equated with “exigencies” by Ahmed Fekry Ibrahim.
These two definitions, derived from fiqh, have little in common with customary law as understood in modern anthropology. Here, customary law refers to a set of long-established, usually unwritten rules of a distinct legal community, which are administered by non-qāḍī, non-state magistrates, including arbiters. Such customary law is often called today “tribal law,” and its existence before the nineteenth century is assumed by projecting backwards modern observations. Whether such a “tribal law” actually existed in the pre-modern period, or whether it was a colonial invention, is a matter of dispute. 
A second problem with the positive value currently placed on custom in pre-modern Islamic law is its supposed neutrality. Modern scholarship, much like medieval fiqh, assumes that customs emerge naturally from within communities. That may hold for linguistic “custom,” that is the meaning of a word at a given context. But customary legal transactions such as share-cropping did not emerge “naturally,” without social and political negotiation. Share-cropping, even if widespread, was likely to benefit one group over another.
To give a current example from the UK, zero-hour contracts of casual labor are widespread in society, and are entered willingly by employees, without direct coercion. Yet those who call for making zero-hour contracts illegal still view them as inherently harmful for workers. Similarly, the permissibility or impermissibility of share-cropping contracts had differential economic implications on landlords and peasants; it was, essentially, a political matter.
Finally, most current scholarship tends to distinguish between customary laws and state law, which is seen as a coercive structure imposed from the top down. Yet such a dichotomy assumes that localized legal communities were isolated from the medieval state, existing in a cohesive bubble that allowed them to develop independently. The historical evidence at our disposal doesn’t seem to support such isolation, even for the most remote communities.
In the coming blog posts, I would like to problematize our understanding of custom and customary law in the pre-modern era. The second post will highlight some excellent recent research on the reception of custom by medieval Muslim jurists, while at the same time arguing that the perspective of the jurists restricts our understanding of the totality of Muslim societies’ legal structures. The third post will examine examples of “tribal laws” in the pre-modern period, focusing on references to systematic disinheritance of women. The fourth blog will trace references to “Bedouin” legal rituals in the pre-modern period, demonstrating that these are neither colonial inventions nor frozen-in-time legacies of a pre-Islamic culture.
 Wael B. Hallaq, Sharīʿa: Theory, Practice, Transformations (Cambridge: Cambridge University Press, 2009), 203.
 Ibid., 316.
 Ahmed Fekry Ibrahim, “Customary Practices as Exigencies in Islamic Law: Between a Source of Law and a Legal Maxim,” Oriens 46, no. 1–2 (January 1, 2018): 222–61, https://doi.org/10.1163/18778372-04601007.
 On colonial administrations re-shaping or inventing customary law in order to create a wedge between Islam and rural groups seen as more amenable to a civilizing project, see Adam Guerin, “Racial Myth, Colonial Reform, and the Invention of Customary Law in Morocco, 1912–1930,” The Journal of North African Studies 16, no. 3 (September 2011): 361–80, https://doi.org/10.1080/13629387.2010.535650.