How does the Islamic legal system function?

What will be an ideal response?

The Islamic legal system is known as Shari'a. It is derived from the following sources, in the order of their importance: (1) the Koran, (2) the Sunna or traditional teachings and practices of the Prophet Muhammad (570–632 a.d.), (3) the writings of Islamic scholars who derived rules by analogy from the principles established in the Koran and the Sunna, and (4) the consensus of the legal community. In the tenth century a.d., three centuries after the founding of Islam, the legal community decided that further improvement of the scholars' analysis of divine law was impossible. They decided at that time to "close the door of ijtihad (independent reasoning)," freezing the evolution of Islamic law. As a consequence, Shari'a judges and scholars may only apply the law as it was set down by the early writers. They may not change, modify, or extend that law.