Since the founding of Islam in the early seventh century (610–32), Islamic law has developed through free markets of jurisprudence, which may be called iswaq al-fiqh or fiqh markets. A fiqh market consists of jurists (muftis), scholars (mujtahids), and followers (ashab). Muftis and mujtahids serve as opiniojurists. They offer juristic opinions on matters of law. When a new legal issue arises that cannot be resolved under the existing body of Islamic law, Muslim opiniojurists offer legal opinions consistent with the Basic Code, the Qur'an, and the Sunnah. These opinions, known as fatwas, compete in the fiqh markets to win over Muslim followers. Each competing opinion may receive some following. An opinion that gains the most Muslim followers becomes a rule of fiqh. Even minority opinions with substantial followings in Muslim communities are treated as rules of fiqh. Each opinion is binding on its followers.

As always, fiqh markets are founded on persuasion, and not coercion. The fiqh rules appeal to logic, common sense, and systemic coherence. While rendering opinions, opiniojurists must demonstrate that an opinion is normatively compatible with the Basic Code and analytically consistent with the existing body of fiqh, just as a judge must demonstrate that a case holding is compatible with the Constitution and the body of law relevant to the case. Opiniojurists are rarely arbitrary or impulsive. They do not convert personal preferences into legal opinions.