Islamic constitutionalism is an integral part of contemporary ijtihad. As its defining attribute, an Islamic constitution submits to supremacy of the Basic Code, the Qur'an and the Prophet's Sunnah. Historically, constitutionalism has not been critical to the advancement of Islamic law. For centuries, Islamic law has developed without any notion of constitutionalism. The classical fiqh markets knew no constitution, nor was their vibrancy dependent on one. The history of law in all legal traditions demonstrates that a viable body of law may come into existence without a written constitution, it may continue to develop without a written constitution, and it may or may not adopt a written constitution as the supreme source of law. Legal systems without written constitutions, however, may gradually develop constitutional conventions that provide political and normative stability. Since 1789, the successful tenure of the US Constitution demonstrates that a written constitution can guide a more reliable evolution of a legal system.

Islamic constitutionalism discussed below is not confined to the rule of law or some other broad underlayment of the government, such as the consultation principle. Nor is it confined to lawful restrictions on the scope of the ruler's authority. These generic concepts are significant elements of modern constitutionalism, and have been parts of almost all Muslim governments since the dawn of Islam. Rule arbitrariness or power absolutism is inherently unlawful under the Basic Code.