"According to the Court's case-law, a difference of treatment is discriminatory, for the purposes of Article 14 of the Convention, if it “has no objective and reasonable justification”, that is if it does not pursue a “legitimate aim” or if there is not a “reasonable relationship of proportionality between the means employed and the aim sought to be realised” (see Abdulaziz, Cabales and Balkandali v. the United Kingdom, judgment of 28 May 1985, Series A no. 94, pp. 35-36, § 72). Moreover, the Contracting States enjoy a certain margin of appreciation in assessing whether and to what extent differences in otherwise similar situations justify a different treatment (see Willis v. the United Kingdom, no. 36042/97, § 39, ECHR 2002-IV). "