The Visigothic Forum Iudicum enjoyed quite exceptional longevity as a code of law put to practical application. Although the geographical range of its authority steadily declined after the eleventh century, it remained the sole comprehensive work of legal codification with more than local relevance from its promulgation in the mid-seventh century to its final replacement by Alfonso X's Siete Partidas in the late thirteenth: a span of over six hundred years. Even in its final phase it is its intended practical applicability that is most striking: Alfonso X's father granted the use of the vernacular version, the Fuero Juzgo as the local law and privilege of recently reconquered Córdoba and Seville. It is as if the Laws of Alfred were still enjoying validity in the reign of Henry VII.

Admittedly, by this stage the Forum had ceased to be enforced in Castille and in Catalonia, and was generally elsewhere supplemented and modified by the proliferation of local fueros. But for a code devised so long previously and in so distant a society the survival and continuing authority of the Forum (also known as Lex Visigothorum) is remarkable. The processes of its modification were also, as far as the evidence can now show us, of relatively recent date, beginning only in the middle of the eleventh century. Indeed the two hundred years before that may well be described as the hey-day of the Forum Iudicum, particularly in terms of our knowledge of how it was applied in practice.