52. Building on this case, the European Commission on Human Rights later refined the principles governing the scrutiny of the elements of an electoral system. Whilst states have a wide margin of appreciation on the introduction of conditions to voting rights, these conditions must satisfy the following criteria: they do not curtail the rights in question to such an extent as to impair their very essence and deprive them of their effectiveness; they must pursue a legitimate aim and the means must be proportional.[27] Both cases referred to (Lindsay, and Polacco and Garafalo) are slightly different in their facts; the first refers to the use of a single transferable vote for the EP elections in Northern Ireland, the latter to the registration requirements for the regional elections in Trentino-Alto Adige. The principles, however, are general enough so as to inspire the examination of other elements of an electoral system.