It is not the intention here to provide a comprehensive review of the principle but just to highlight the most critical areas. A distinction, exclusion, restriction or preference is compatible with the principle of equality when (a) it has objective and reasonable justification; (b) it pursues a legitimate aim under human rights law;and (c) there is a reasonable relationship of proportionality between the means employed and the aim sought to be realized.48 Differences in treatment that comply with the criteria mentioned above are not discriminatory and do not infringe the principle of equality and non-discrimination. Thus, discrimination may arise not only from an explicit unequal treatment in the law but also from laws that at face value are neutral but in practice have a disproportionate impact on the enjoyment or exercise of rights on an equal footing.49 For example, a law stating that the surviving partner of a heterosexual relationship is entitled to a pension would indirectly discriminate against same-sex couples.