244 EARLY MEDIEVAL SPAINroots of whose status is impossible to trace, were the principal land-
owners in the frontier regions, although there was also a substantial
number of smaller property-owners of free status encouraged to settle
there in the periods of repopulation by special concessions.^31 For if
the towns in the Duero valley and Castille, reoccupied or newly cre-
ated by the Asturian and Leonese kings, were to be made into per-
manent and secure settlements, as was needed if the regions were to
be retained successfully, a larger population was required. In the
conditions that existed in these marcher zones tangible inducements
were often necessary to bring in new settlers to occupy and defend
the towns and related countryside. Considerable concessions were
made by the kings and great lords in respect of autonomy and the
privileges granted to the citizenry in these frontier towns. These gen-
erally varied from place to place and represent individual agreements
made between the citizens and their overlord and these were generally
in written form. Such charters of municipal rights, called fueros, could
also include modifications of existing law and special legal regulations
that then became part of the privileges of the citizenry. Fueros are
known from later reissues to have been granted to Burgos and
Castrojeriz in the tenth century, and the extant ones of Leon date
from the early eleventh. Some of these early fueros became models for
later ones. Similar practices were followed from the eleventh century
in the kingdoms of Navarre and Aragon, and the confirmation of
municipal fueros by successive kings became an important feature of
Spanish political life. One consequence of the growth of fueros was
the increasing modification of the application of the law of the Forum
Iudicum or Fuero Juzgo as it became in the vernacular. Castille in par-
ticular became a stronghold of localised law and custom, as opposed
to Leon where the Fuero Juzgo remained generally in force until the
thirteenth century. Fueros did not necessarily have to be royal conces-
sions, as they could be granted by any landowner to his dependants.
The tenth-century counts of Castille made the earliest such grants in
that region. In addition, special classes of subjects might have their
own fueros. Thus by the reign of Alfonso VI Jews in Leon had separate
fueros from those of the Christians.^32
The general fueros of Leon first appear in the ordinances of a
council held in the city by Alfonso V in 1020.^33 It is conceivable that
some of the regulations and concessions there written already existed
and that the council was codifying current practice and committing
it formally. The decrees relating to Leon and the rights of its citizens