Roman law was first the local law of a small central Italian city-state. As the political boundaries of that state expanded, so did its law, until by the early centuries of our era its influence was widespread over and beyond the Mediterranean basin. Important evidence revealing the application of Roman law at local level has recently been dug up in southern Spain; the Roman lawyer and administrator Papinian is said to have been at the northern British capital York assisting the Emperor in dispensing justice in AD 208; and papyri from Egypt and the Arabian desert indicate the extent of penetration of Roman legal notions even in areas of strong local traditions. Conveyances written on wood in Transylvania testify to a near-obsessive desire to comply with metropolitan standards.

The Roman legal tradition was characterised not so much by its substantive rules as by its intellectual methodology. Between about 100 BC and AD 250 the Roman jurists developed techniques of analogical and deductive reasoning which produced a jurisprudence of enormous refinement and sophistication. When the Emperor Justinian caused the substantial extracts from the writings of these classical jurists to be collected together in the early sixth century AD, he ensured the survival of their thought into subsequent ages. His Digest remains the finest monument of any legal culture.

As the political fortunes of the Roman state waned, so did its direct legal influences.