Imperium in imperio

Many commentators on the Constitutions of Clarendon have ascribed Becket's motive and goal for the stance which he took, upon his appointment as Archbishop of Canterbury and at the Council of Clarendon in 1164, as one of his wishing to set up an imperium in imperio, a "state within a state", a "kingdom within a kingdom". The Church was in essence only partially subject to Henry's laws if at all. The Church operated its own court system, which answered not to Henry but to the Pope. The Church had its own legal system

References

Charles Oman (1 April 1972). History of England. Ayer Publishing. pp. 101–. ISBN 978-0-8369-9920-4.

Henry II - 9th Edition of Encyclopedia Britannica

Henry II, King of England (1133-1189)

The Constitutions of Clarendon were an essential part of this scheme, designed to bring the clergy, as well as other classes of the nation, under the rule of law, and to prevent an ecclesiastical " imperium in imperio."

Assize of Clarendon - Wikipedia

Finally, there was the long-standing difficulty involving the Church, which culminated in the murder of Thomas Becket, the Archbishop of Canterbury. The problem for the King was that the Church acted like an imperium in imperio, a "kingdom within a kingdom", only partially subject to Henry's laws if at all. The Church operated its own court system, which answered not to Henry but to the Pope; it was a large landowner and a powerful vested interest. Henry wished to establish a system of justice that would enlarge the power of the Crown at the expense of the clergy.

Philip Schaff. History of the Christian Church, Volume V: The Middle Ages. A.D. 1049-1294.. CCEL. pp. 162–. ISBN 978-1-61025-044-3.

Robert Montagu (lord.) (1864). "Locke's Theory". The four experiments in Church and State and the conflicts of Churches. Longman, Green, Longman, Roberts, & Green. pp. 25–.

Robert Montagu (lord.) (1864). The four experiments in Church and State and the conflicts of Churches. Longman, Green, Longman, Roberts, & Green. pp. 36–.

Walter Farquhar Hook (1846). An ecclesiastical biography, containing the lives of ancient fathers and modern divines, interspersed with notices of heretics and schismatics. pp. 141–. 

The Christian remembrancer. Printed for F.C. & J. Rivington. 1859. pp. 164–.

The North British Review. 1854. pp. 383–.

Richard Hurrell Froude; James Bowling Mozley (1839). Remains of the Late Reverend Richard Hurrell Froude: v. 2. History or the contest between Thomas à Becket, archbishop of Canterbury, and Henry II, king of England, chiefly consisting of translations of contemporary letters. J. G. & F. Rivington. pp. 393–.


Alternative Views

Ullman, Walter. The Relevance of Medieval Ecclesiastical History. CUP Archive. pp. 1–. GGKEY:0ZHL6EEPNHJ.  An Inaugural Lecture by Walter Ullmann Professor of Medieval Ecclesiastical History University Of Cambridge 

Stephen Harris; Bryon L. Grigsby (24 December 2007). Misconceptions About the Middle Ages. Routledge. pp. 1–. ISBN 978-0-203-93242-1.

The Two Laws in England: The Later Middle Ages by W.R. Jones 

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