Royal jurisdiction was to play a vital role in integrating England politically, for the law formed the essence of government and was a major force for connectivity. Enjoying a virtual monopoly on criminal proceedings across the kingdom, the Crown's judicial agencies reached to the furthest corners of Cornwall in a standard (common) form. In sharp contrast to the position in parts of Wales, where distinct Welsh and English judicial systems prevailed, the common law regarded all Cornishmen and women as English. In Cornwall the peace was the king's peace, symbolically drawing the county into the realm.

Across the fourteenth century the scope of both statute and common law greatly expanded throughout England. Royal courts increasingly drew pleas concerning debt into their competence, while the king passed and enforced a burgeoning number of statutes. Statute law came to regulate spheres of life which had never before fallen within the purview of royal justice, among these wage levels. Unsurprisingly, procedural and institutional changes were to match these developments. In the thirteenth century the eyre had formed one of the main instruments of royal government, the justices visiting each county every seven years or so and, once there, hearing all cases concerning that locality. Since the eyre collapsed under its own weight in the early-fourteenth century, however, the Crown had to find new mechanisms of enforcing its legal prerogatives. The solution it alighted upon involved the justices of the peace. In the years before 1330 the keepers of the peace had possessed only modest authority, but by the 1360s their successors, the justices of the peace, had amassed considerable judicial powers. It followed that the range of responsibilities that the Crown devolved to these local officers greatly increased. These local agents, however, never achieved a monopoly on the local dispensation of justice. Bringing with them national practices and precedents in both civil and criminal matters, the central court justices who sat on commissions of assize and gaol delivery in the provinces and on the quorum of each county bench closely supervised the local magistracy. In this way, the Crown and the shires together forged a remarkably integrated system of royal jurisdiction across the realm, a more pervasive ‘national’ legal culture.