4 12. Although the two Vienna Conventions on the Law of Treaties prohibit the acceptance of reservations incompatible with the object and purpose of the treaty at issue, they leave, however, various questions without answers. The criterion of the compatibility is applied in the relations with the States which effectively objected to the reservations, although such objections are often motivated by factors - including political - other than a sincere and genuine concern on the part of the objecting States with the prevalence of the object and purpose of the treaty at issue. For the same reason, from the silence or acquiescence of the States Parties in relation to certain reservations one cannot infer a belief on their part that the reservations are compatible with the object and purpose of the treaty at issue. 13. Such silence or acquiescence, moreover, appears to undermine the application of the criterion of the compatibility of a reservation with the object and purpose of the treaty. And the two Vienna Conventions referred to are not clear either, as to the legal effects of a non-permissible reservation, or of an objection to a reservation considered incompatible with the object and purpose of the treaty at issue. They do not clarify, either, who ultimately ought to determine the permissibility or otherwise of a reservation, or to pronounce on its compatibility or otherwise with the object and purpose of the treaty at issue. 14. The present system of reservations permits even reservations (not objected) which hinder the possibilities of action of the international supervisory organs (created by human rights treaties), rendering difficult the realization of their object and purpose. The above-mentioned Vienna Conventions not only fail to establish a mechanism to determine the compatibility or otherwise of a reservation with the object and purpose of a given treaty 4, but - even more gravely - do not impede either that certain reservations or restrictions formulated (in the acceptance of the jurisdiction of the organs of international protection) 5 come to hinder the operation of the mechanisms of international supervision created by the human rights treaties in the exercise of the collective guarantee. The present Blake case will remain as a sad and disconcerting illustration in this respect. 15. The present system of reservations, reminiscent of the old pan-American practice, rescued by the International Court of Justice and the two Vienna Conventions on the Law of Treaties, for having crystallized itself in the relations between States, not surprisingly appears entirely inadequate to the treaties whose 4. As neither the afore-mentioned Vienna Conventions, nor - prior to them - the cited Advisory Opinion of the International Court of Justice on Reservations to the Convention against Genocide, define what constitutes the compatibility or otherwise (of a reservation) with the object and purpose of a treaty, the determination is left to the interpretation of this latter, without it having been defined either on whom falls that determination, in what way and when it should be made. At the time of the adoption of that Advisory Opinion (1951), neither the majority of the Hague Court, nor the dissenting Judges on the occasion, foresaw the development of the international supervision of human rights by the conventional organs of protection; hence the insufficiencies of the solution then advanced, and endorsed years later by the two Vienna Conventions on the Law of Treaties referred to. 5. There is a distinction between a reservation stricto sensu and a restriction in the instrument of acceptance of the jurisdiction of an international supervisory organ, even though their legal effects are similar.