Both these books are elegantly written, clearly ordered, extensively referenced and meticulously examined. With regard to Islam, together they present two sides of a coin. Norman Doe examines the structures and rules by which Judaism, Christianity and Islam order themselves in Britain, and with detailed analysis he finds substantial similarities between the organisation of the three Abrahamic faiths. Aiming to test recent public assumptions about religious laws in Britain and supposed differences between the faiths, he charts the different dispositions of each faith's denominations: Orthodox, Reformed, Liberal and Conservative Judaism; Roman Catholic, Anglican, Free Church and Baptist Churches; Sunni Islam, with its four schools of law (Hanafi, Maliki, Shafi'i and Hanbali), and Shia Islam with its Jafari School recognising four sources of Islamic law (the Qur'an, Sunnah, consensus and human reason). At least 96 per cent of Britain's 2.7 million Muslims are Sunni, with 2 per cent Shi'a; of around 1,600 mosques, about 1,520 are Sunni.

Within the context of classical religious (primary law) sources and texts, Doe considers the modern (secondary) regulations that each faith has evolved, together with their ‘soft-law’ codes of conduct, policies and guidelines, and even different detailed provisions made by local synagogues and mosques in various parts of Britain. He covers and compares their objects, their governance, their handling of disputes, the qualification, duties and rights of membership, the rites of passage, the ownership of property, and the relationship with the State and its laws.

Doe's evidence refutes claims made, under pressure of a media storm, that ‘Shari'a law has no jurisdiction in England and Wales’ (Bridget Prentice MP, Ministry of Justice, 2008) and that ‘you can only really cope with one philosophy of law within a jurisprudential system’ (Archbishop Justin Welby, 2017). Doe reveals a more nuanced accommodation in which the State already recognises religious legal instruments consistent with civil law, and in which faith organisations seek to avoid inconsistencies with religious laws. He offers a substantial draft, ‘Towards a charter of Abrahamic law’, called for by the Woolf Commission in 2015 and articulating principles of religious law common to all three faiths.

Khaled Bashir lifts the curtain on a wider picture, stretching from Baghdad to Toledo, examining the foundations of Islamic law governing relations between nations in peace and at war. Importantly, his focus is on the eighth-century (ad) Islamic jurist Muhammad Ibn Al-Hasan Al-Shaybani, who travelled widely and wrote prolifically but has been neglected by Western scholars. Unfortunately many of Al-Shaybani's works have been lost, but his first book, Al-Siyar Al-Saghir, has been the foundation of much later thinking on Siyar, a term which Bashir thinks is best interpreted as ‘international law’, although that did not yet exist as a separate field of study, and although the Arabic term itself has a wider reach. That ‘Shorter Book of International Law’ was succeeded by a grander book, Al-Siyar Al-Kabir, encompassing a greater range of matters than war and peace but no longer available in its entirety. Bashir's researches into commentaries upon it, not least a handwritten manuscript at Leiden University dated 1422 ad, are the basis of his work and his insistence that it is urgent to rediscover Al-Shaybani's thought.

A devout Libyan Muslim and international lawyer, previously working both practically and in research in Tripoli but for some years now teaching in the University of Aberdeen, Bashir sets himself to show that subsequent Islamic jurists inadequately represented Al-Shaybani's humanitarian vision. He confronts the view of some legal historians that there was almost a thousand-year gap between Greek and Roman juristic teaching and modern Western thought and, with meticulous detail, compares Al-Shaybani's thoughts and methods with the work of Augustine before him and of Gratian, Aquinas, Vitoria and Grotius several centuries later. The closest comparisons are with the Spaniard Vitoria (1483–1548), who can hardly have been unaware of Islamic writings, and with the Dutch jurist and statesman Grotius, the ‘father of international law’, who wrote The Law of War and Peace in Paris in 1625. Grotius has a whole chapter comparing and contrasting Islam to Christianity and Muhammad with Jesus and, although his comments show much misunderstanding, the depth of his knowledge of Siyar and of rules in the ancient Middle East make it likely that he knew of Al-Shaybani's work.

As early as the twelfth century, Baghdad's libraries held more than 850,000 volumes; in the mid-thirteenth century the royal library at Cordoba contained 400,000, while the University of Paris, the largest mediaeval library in Christian Europe, had just 1,017 in 1289. By comparison, Thomas Bodley's re-founding of the University of Oxford's Duke Humfrey's Library grew from only 2,000 books in 1598 to 16,000 in 1620. The commentaries on Aristotle by the twelfth-century Cordoba jurist Averroes were the source of inspiration for Aquinas, while in Toledo Arabs, Jews and Greeks worked with Spaniards, Frenchmen and Germans, with Slavs from the Balkans and Englishmen as well. Western Europe drew on the flow of knowledge through Muslim Sicily and Spain.

For Muslim scholars, law, not theology, was the master science. God had revealed himself in the Qur'an not in his nature but as law and command. This gives closer parallels between Islam and Judaism than with Christianity, though it is noteworthy that sharia literally means ‘the way’ and that early Christians were known as ‘followers of the Way’ (Acts 9:2). While Muslim scholars readily acknowledged the translation of Greek and Persian books on science and philosophy, there is little evidence that they translated non-Islamic books on jurisprudence. The Caliph of Baghdad's great research institute was founded a century after Al-Shaybani was writing, referencing the ideas of other jurists; none was non-Islamic.

Siyar springs from both the Qur'an and from the Sunna, the prophetic tradition (hadieth) of inspired sayings and practices of Muhammad, but, while Christian writers such as Augustine and Aquinas ranged from the New Testament to the Hebrew Scriptures seeking verses to support conclusions on just war, for instance, the Qur'an must be read not as individual provisions but as an integrated whole. Where there is uncertainty, a consensus (ijma'a) is required from Islamic scholars; a qualified jurist (one versed in all branches of Qur'anic sciences and precedents) may reach an opinion by analogy (quias), though this could be refuted by consensus. This gave scope for Al-Shaybani to introduce his own opinion into Siyar, yet he remained ready to quote from and defer to the views of others. The divine law was paramount, the task of the Islamic jurist being not to make laws but to discover and expound the law of God, not something to be overturned or altered by any parliament or legislature.

Though judged to have developed an entirely secular theory of natural law, Grotius also defined natural law as reason applied to understanding the will of God, and Vitoria believed that, if anything is lawful or unlawful according to divine and natural law, it cannot be rendered otherwise by human law. Grotius, however, attempted to distinguish between what is allowed by nature and what is permitted to Christians: their additional knowledge, beyond what natural reason provides, gives them limits not binding other nations.

Bashir explains that, while scholars have often mistaken the classical division of the world into dar-al-harb and dar-al-Islam to represent a hostile separation, in Al-Shaybani's thought the two terms merely distinguish the lands of foreigners from lands under Islamic law, much like the pax Romana. Where Augustine's separation between civitas terrenae and civitas dei was theological, Al-Shaybani's division is juristic. Jihad can indicate a war of words or intellects rather than fighting. Writing when war was a constant feature of the political landscape and when ancient Rome had considered itself permanently at war with any state with which it had no treaty of friendship or alliance, Al-Shaybani's detailed writing on peace and peace-making is a substantial, and integrated, part of his book. For him, war must be the last resort, permissible only to secure the state or, in extremely qualified circumstances, when the preaching of Islam's message to all humanity has been hindered. Bashir contrasts this with modern Western claims that forcing regime change, imposing democracy and defending human rights (as defined by the United Nations) can be justified, regardless of a country's culture and religion.

Aquinas built on Augustine to require three conditions before war could be called ‘just’ (better ‘justified’): authority of the sovereign, just cause and rightful intention. Al-Shaybani too required rightful intention, specifically for no other cause but serving God and not for worldly gains. Grotius and Vitoria each juggled with practical questions and exceptions, differing as to the treatment of non-combatants and those in neutral countries. Bashir scrupulously explores the many permutations of the arguments, noting how interpretations of both ‘just war’ and jihad have fluctuated down the centuries. None is more detailed than Al-Shaybani with regard to the treatment of prisoners, whether Muslims in enemy hands or enemy prisoners held by Muslims, the possibilities of enslavement or execution, ransom or exchange, and the handling of spoils. Twenty-first-century treatment of prisoners in Abu Ghraib or Guantanamo contrasts starkly with the respect for prisoners of war on which Al-Shaybani insists.

Among Al-Shaybani's innovative thoughts was to consider individuals as subjects of international law, an idea which only gained ground in Europe in the detailed rules produced by Vitoria on the rights of individuals to travel where they wished, as long as they were not harmful to a host nation. Al-Shaybani worked out detailed rules of ama'an (a pledge of safe conduct) for travellers in a Muslim state, even when it was at war with their own. So long as they believed, even incorrectly, that they had been given that pledge, which could be given by any adult Muslim, they should be respected and safe from harm. In 1943 Hersch Lauterpacht declared that ‘the individual human being … is the ultimate unit of all law’; as Philippe Sands has shown in East West Street, Lauterpacht and his fellow refugee Jew from Lvov, Rafael Lemkin, agreed on the value of a single human life and on the importance of being part of a community, although Lauterpacht, with his formulation of crimes against humanity, and Lemkin, with his concern to prevent genocide, disagreed whether to focus on the individual or the group. Had Al-Shaybani's work been available to them, each might have valued it.

Bashir builds on Oliver O'Donovan's call for a richer and more coherent system of international law founded on mutual respect among nations under natural law in the classical sense represented by Grotius, rather than the hegemonic claim of one or two Western countries to represent the values of the whole of humanity. The contemporary state-sponsored system is seen by some Western philosophers as morally bankrupt and politically corrupt, serving too closely Western economic interests. One-sixth of the world's population would respond to Islamic international law, though it would be a mistake to suppose that Al-Shaybani represents all Muslim jurists any more than Augustine, Grotius or Vitoria represents all Europeans or all Christians. However, there is room for greater appreciation of the diverse religious and philosophical foundations of faiths rather than seeking to force all into one secular mould.

Here, Bashir and Doe come close together, as Doe sets out his convergent principles of the Abrahamic faiths. They chime also with the plea in this Journal that recognised and properly regulated religious tribunals (Beth Din in the USA, the Muslim Arbitration Tribunal in the UK) can better adapt and re-interpret their own traditions in order to comply with important societal demands, free from patriarchalism.Footnote ² Religious arbitration, driven underground, would not be subject to any sort of judicial review. As Doe makes plain, women need sharia councils able to grant divorces which can be recognised as religious by their own communities or in other lands, as well as civil jurisdiction to adjudicate on children and financial assets.

Both writers deserve thanks for their painstaking and complementary contributions to a subject of increasing urgency.