There are 27 municipalities with language facilities in Belgium which must offer services to residents in Dutch, French or German, in addition to their official languages. All other municipalities – with the exception of those in the Brussels region which is bilingual – are unilingual and only offer services in their official languages, either Dutch or French.
Belgian law stipulates that:
There were three language areas as from the 31 July 1921 law: the Dutch-speaking Flemish area, the French-speaking Walloon area, and the bilingual area of Brussels (capital city). These language areas of 1921 actually had no institutional translation in the structure of the Belgian state, then still constitutionally divided into provinces and municipalities. Thence a French-speaking unilingual municipality could, for instance, be part of the province of West Flanders.
The Belgian law of 28 June 1932, on the use of languages for administrative matters based the language status of every Belgian municipality on the decennial census that included, since 1846, several language questions about the knowledge as well as the day-to-day practice. The criterion to belong to the Flemish- or Walloon-language area was the a threshold of 50%; whereas with a threshold of 30% the municipal authorities had to offer services in the minority language as well. A municipality could ask the government to change its linguistic status by a royal decree only after a census showed a passage over the 30% or 50% threshold.
The German- and Luxembourgish-speaking minorities in Eastern Wallonia were not mentioned in the 1921 or 1931 laws. The German-speaking minority was mostly settled in the 'Eastern Cantons', several Prussian municipalities ceded to Belgium by the 1919 Treaty of Versailles and administered from 1920 to 1925 by a Belgian military High Commissioner. There was, and still is, a Luxembourgish-speaking minority in some municipalities bordering the Grand Duchy of Luxembourg.