Case “relating to certain aspects of the laws on the use of languages in education in Belgium” V. Belgium (MERITS) (Application no 1474/62; 1677/62; 1691/62; 1769/63; 1994/63; 2126/64)

10. (..)  It is important, then, to look for the criteria which enable a determination to be made as to whether or not a given difference in treatment, concerning of course the exercise of one of the rights and freedoms set forth, contravenes Article 14 (art. 14). On this question the Court, following the principles which may be extracted from the legal practice of a large number of democratic States, holds that the principle of equality of treatment is violated if the distinction has no objective and reasonable justification. The existence of such a justification must be assessed in relation to the aim and effects of the measure under consideration, regard being had to the principles which normally prevail in democratic societies. A difference of treatment in the exercise of a right laid down in the Convention must not only pursue a legitimate aim: Article 14 (art. 14) is likewise violated when it is clearly established that there is no reasonable relationship of proportionality between the means employed and the aim sought to be realised.