19 June 1999,
The Spanish Supreme Court declared it illegal for southern municipalities to speak exclusively in Basque. In a judgment contrary to the ordinance adopted by the City of Aizarnazabal in 1992, it was stated that this was discriminatory. According to the census, 541 out of every 544 inhabitants were Basques and only three were Castilan-speaking. Although these people never complained – they were sent letters in an understandable way or guaranteed the possibility of processing in Spanish – the Spanish High Court of Justice also became involved in the more Basque peoples to impose Spanish.
Source:
Mikel Arrieta considers it illegal for municipalities to operate only in Euskera (Euskaldunon Egunkaria, 20 June 1999).