The ill-fated 2012 languages law in Ukraine (proposed by the Party of Regions, but eventually found unconstitutional by Ukraine's supreme court)
allowed the use of minority languages in courts, schools and other government institutions in areas of Ukraine where the national minorities exceed 10% of the population.
Was this modelled after some laws in countries of Europe (incl. Russia)? I.e. are there countries in Europe with a law with a similar provision based on a percentage, and is it this low (10%) or close to that, say <20%?