The caliphs  and eventually the sultans who came to rule once the caliphate lost most of its worldly influence  still had plenty of power. They handled foreign affairs more or less at their discretion. And they could also issue what were effectively administrative regulations  provided these regulations did not contradict what the scholars said Shariah required. The regulations addressed areas where Shariah was silent. They also enabled the state to regulate social conduct without having to put every case before the courts, where convictions would often be impossible to obtain because of the strict standards of proof required for punishment. As a result of these regulations, many legal matters (perhaps most) fell outside the rules given specifically by Shariah.

The upshot is that the system of Islamic law as it came to exist allowed a great deal of leeway. That is why today’s advocates of Shariah as the source of law are not actually recommending the adoption of a comprehensive legal code derived from or dictated by Shariah  because nothing so comprehensive has ever existed in Islamic history. To the Islamist politicians who advocate it or for the public that supports it, Shariah generally means something else. It means establishing a legal system in which God’s law sets the ground rules, authorizing and validating everyday laws passed by an elected legislature. In other words, for them, Shariah is expected to function as something like a modern constitution.

The Rights of Humans and the Rights of God

So in contemporary Islamic politics, the call for Shariah does not only or primarily mean mandating the veiling of women or the use of corporal punishment  it has an essential constitutional dimension as well. But what is the particular appeal of placing Shariah above ordinary law?

The answer lies in a little-remarked feature of traditional Islamic government: that a state under Shariah was, for more than a thousand years, subject to a version of the rule of law. And as a rule-of-law government, the traditional Islamic state had an advantage that has been lost in the dictatorships and autocratic monarchies that have governed so much of the Muslim world for the last century. Islamic government was legitimate, in the dual sense that it generally respected the individual legal rights of its subjects and was seen by them as doing so. These individual legal rights, known as “the rights of humans” (in contrast to “the rights of God” to such things as ritual obedience), included basic entitlements to life, property and legal process  the protections from arbitrary government oppression sought by people all over the world for centuries.

Of course, merely declaring the ruler subject to the law was not enough on its own; the ruler actually had to follow the law. For that, he needed incentives. And as it happened, the system of government gave him a big one, in the form of a balance of power with the scholars. The ruler might be able to use pressure once in a while to get the results he wanted in particular cases. But because the scholars were in charge of the law, and he was not, the ruler could pervert the course of justice only at the high cost of being seen to violate God’s law  thereby undermining the very basis of his rule.

In practice, the scholars’ leverage to demand respect for the law came from the fact that the caliphate was not hereditary as of right. That afforded the scholars major influence at the transitional moments when a caliph was being chosen or challenged. On taking office, a new ruler  even one designated by his dead predecessor  had to fend off competing claimants. The first thing he would need was affirmation of the legitimacy of his assumption of power. The scholars were prepared to offer just that, in exchange for the ruler’s promise to follow the law.

Once in office, rulers faced the inevitable threat of invasion or a palace coup. The caliph would need the scholars to declare a religious obligation to protect the state in a defensive jihad. Having the scholars on his side in times of crisis was a tremendous asset for the ruler who could be said to follow the law. Even if the ruler was not law-abiding, the scholars still did not spontaneously declare a sitting caliph disqualified. This would have been foolish, especially in view of the fact that the scholars had no armies at their disposal and the sitting caliph did. But their silence could easily be interpreted as an invitation for a challenger to step forward and be validated.