In much of Continental Europe, the laws were based on those inherited from the Roman Empire, i.e. Roman (or Civil) Law. In every country, the laws had been altered and adapted in response to local customs and circumstances. The French legal theorists Jacques Cujas (1520-90) and Francis Duaren (François Douaren) (1509-99) even argued that custom was the supreme form of law.

However, it was in England that custom played the most important role in shaping law. The English system of Common Law was relatively unaffected by Roman Law - in England, law was not codified, but determined by judges on the basis of earlier decisions (precedent) and custom.

Common lawyers were important in English society - they made up a large proportion of those sitting in the House of Commons. Sir Edward Coke and many other common lawyers shared a political ideology based on the notion that ancient custom (as interpreted by common lawyers) was superior to the king and to all other forms of law.
A classic expression of common law thinking was given by Thomas Hedley in a Speech in Parliament in 1610

Common law thinking was a largely conservative ideology designed to protect the status quo from the intrusion of government and was as opposed to doctrines of popular sovereignty as to those of royal absolutism. The conservative theorist, Edmund Burke (1729-97) preserved many of the elements of common law thought when he lauded the "wisdom of our ancestors," expressed "no very exalted opinion of the virtue of paper government," and insisted that "to innovate is not to reform."

 

Sir John Fortescue was Chief Justice of the King's Bench from 1442. He sided with Henry VI in the Wars of the Roses and when Henry was defeated and deposed, Sir John fled abroad.

While in exile in France, Sir John Fortescue wrote De laudibus legum Angliae and The Governance of England, a work that compared English and French society and government.

Fortescue asserted that the English form of government - because it was a "regimen politicum et regale" (i.e. a constitutional monarchy) - was superior to foreign forms of monarchy such as the French. Because taxation and legislation required the people's consent in England, the whole population was free and prosperous. People were motivated to defend the country from foreign foes and to take civic responsibilities, like jury service, seriously. Jurors, being prosperous free farmers, could not easily be bribed. In France, by contrast, the jury system would not work, because the downtrodden French peasantry could easily be bribed or overawed by wealthy lords.

Fortescue took many ideas from Saint Thomas Aquinas and from Leonardo Bruni (1369-1444), but his stress on the excellence of the English constitution was his own.

Sir John Davies was not only a legal theorist, a Member of Parliament, and Solicitor General for Ireland, but a distinguished poet.

Davies introduction to his Irish Law Reports provided a classic expression of the the common law outlook.

Unlike Sir Edward Coke, Davies believed that the king had many extra-legal prerogatives (i.e. emergency powers) - it was simply that English monarchs had the sense and moderation only rarely to exercise them.

Another lawyer who took a very high view of the royal prerogative was Sir Francis Bacon. Bacon was an advocate of law reform, but was more concerned to advance scientific knowledge.

The most important of the common law theorists was Sir Edward Coke. He was widely recognized by contemporaries as the greatest living lawyer. Related by marriage to the William and Robert Cecil, he was steadily promoted, becoming Solicitor General in 1592, Attorney General in 1593, and Lord Chief Justice of the Common Pleas in 1606; in 1613 he was transferred to the Chief Justiceship of the King's Bench, which was technically a promotion but meant a drop in salary..

Coke pronounced on a series of cases of great constitutional importance

 Coke's frequent opposition and general audacity exasperated James, who believed that the King's Chief Justices should share the King's interests, and in 1616 he dismissed Coke from the judiciary. Coke continued to oppose many crown policies - he was imprisoned after the Parliament of 1621, and took a major part in drawing up the Petition of Right.

Yet Coke was extremely ambitious, and tried to regain royal favor by forcing his daughter into marriage with Sir John Villers  (brother of the royal favorite George Villiers (later Duke of Buckingham). He never regained his post as Chief Justice, though he was intermittently readmitted as an advisor; after 1621 he fell altogether from royal favor.

Coke's writings were generally regarded as authoritative  both by contemporaries and later lawyers and constitutional theorists in England and America.
In a series of thirteen Reports Coke summarized the arguments in contemporary cases spinning them in his own way. His Institutes (which appeared in four parts) formed a comprehensive outline of English law.