Uṣūl al-fiqh (Arabic: أصول الفقه‎) (literally: legal theory) is the study of the origins, sources, and principles upon which Islamic jurisprudence (or Fiqh) is based. In the narrow sense, it simply refers to the question of what are the sources of Islamic law. In an extended sense, it includes the study of the philosophical rationale of the law and the procedures by which the law applicable to particular cases is derived from the sources.

In classical Sunni Islam, there are four major sources of jurisprudence: the Qur'an, the Sunnah, ijma' (consensus), and qiyas (analogy).

There is some dispute amongst the Sunni jurists regarding ijma' and qiyas. The Zahirites in particular reject all forms of qiyas, and Dawud al-Zahiri, Abu Hanifa and Ahmad bin Hanbal only accepted ijma' al-sahaba (consensus of the companions of Muhammad).

Abu 'Abd Allah al-Shafi'i (767-819) documented a systematized form of usul, developing a cohesive, systematic procedure for legal reasoning(ijtihad). His approach contrasted with the Hanafite methodology that determined the sources from the sayings and rulings of the companions and successors. Furthermore, he raised the Sunnah to a place of prominence and restricted its legal use. According to al-Shafi'i, only practices directly passed down from Muhammad were valid, eliminating the legitimacy of practices of Muhammad's followers. Prior to al-Shafi'i, legal reasoning included personal reasoning thus suffering from inconsistency. al-Shafi'i is probably best known for writing Al-Risala, a prime example of applying logic and order to Islamic jurisprudence.

Suhaib Webb is a contemporary American-Muslim educator, activist, and lecturer. He is currently the imam of the Islamic Society of Boston Cultural Center (ISBCC), the largest mosque in the New England area.

He was born William Webb in 1972 in Oklahoma to a Christian family, including a grandfather who served as a preacher. At age 14, he lost interest in religion going through a self-described spiritual crisis. He also began engaging in delinquency by joining a local gang, was involved in a drive by shooting, and became a successful local Hip-Hop DJ and producer, making records with various artists.

After converting to Islam in 1992, Webb left his career as a DJ and studied at the University of Central Oklahoma, where he graduated with a Bachelor's degree in Education. He also studied privately under a Senegalese Sheikh, learning enough Islam and Arabic to become a community leader in Oklahoma City, where he was hired as Imam at The Islamic Society of Greater Oklahoma City. He simultaneously started teaching at Mercy School, an Islamic K-12 school in Oklahoma City.

Anjem Choudary (Urdu: انجم چودری; born 1967 in England) is a British former solicitor, and, before it was proscribed, spokesman for the Islamist group Islam4UK. He is married, has four children, and lives in Ilford, London.

Choudary studied medicine at the University of Southampton before switching to law. He became a solicitor, and chairman of the Society of Muslim Lawyers. He later met Omar Bakri Muhammad, and the two helped form the Islamist organisation, al-Muhajiroun. The group organised several anti-Western demonstrations, including a banned protest march in London for which Choudary was summoned to appear in court. Al-Muhajiroun was a controversial organisation, which was later disbanded following the UK government's decision to ban it. Choudary was present at the launch of its intended successor, Ahlus Sunnah wal Jamaah, and later helped form Al Ghurabaa, which was also banned, before he became the spokesman for Islam4UK.

Choudary is a vocal critic of the UK's involvement in the wars in Iraq and Afghanistan, and has praised the terrorists involved in the attacks of 11 September 2001, and 7 July 2005. He believes in the implementation of Sharia Law throughout the UK, and marched in protest at the Jyllands-Posten cartoons controversy, following which he was prosecuted for organising an unlawful demonstration. He was also investigated, but not charged, for his 2006 comments regarding Pope Benedict XVI. Choudary receives little support from the mainstream UK Muslim population and has been largely criticised in the media.