The date is indeterminate because the text of the fuero is not preserved, but it would clearly have been founded in the same period as the nearby Puebla de Arganzón and Vitoria-Gasteiz.

Following its incorporation into Castile, a good portion of Álava was organized into behetrías, at least nominally choosing their own local leader.

However, Treviño and Vitoria were not included in this plan, remained directly under the control of the monarch as part of the royal seigneury.

[3] In 1332, at the Campo de Arriaga the Brotherhood of Álava formally recognized the royal seigneury over Treviño and its surrounding territories.

Thus Treviño found itself generally left to its own devices as the seat of a noble family, sitting in the middle of Álava, surrounded by communities operating under the more egalitarian fueros typical of the Basque Country.