What does federal law come from?
Federal law originates with the Constitution, which gives Congress the power to enact statutes for certain limited purposes like regulating interstate commerce. The United States Code is the official compilation and codification of the general and permanent federal statutes. Many statutes give executive branch agencies the power to create regulations, which are published in the Federal Register and codified into the Code of Federal Regulations. Regulations generally also carry the force of law under the Chevron doctrine. Many lawsuits turn on the meaning of a federal statute or regulation, and judicial interpretations of such meaning carry legal force under the principle of stare decisis.
Much of the study in the madrasah college centred on examining whether certain opinions of law were orthodox. This scholarly process of "determining orthodoxy began with a question which the Muslim layman, called in that capacity mustaftī, presented to a jurisconsult, called mufti, soliciting from him a response, called fatwa, a legal opinion (the religious law of Islam covers civil as well as religious matters). The mufti (professor of legal opinions) took this question, studied it, researched it intensively in the sacred scriptures, in order to find a solution to it. This process of scholarly research was called ijtihād, literally, the exertion of one's efforts to the utmost limit."