E. Hierarchy of the Convention in the legal system of States

In States where the Convention is directly applicable, it has been assigned different levels within the domestic hierarchy of laws. Costa Rica, for example, recognizes conventions as being on the same level as the Constitution. In Argentina, a bill was presented to parliament so that the Convention would be recognized as being at constitutional level, similar to other human rights treaties. In several States, such as Croatia, Mali, Mexico and Niger, international human rights treaties to which they are a party are regarded as standing above national laws.

Human rights treaty bodies have often requested clarity regarding the place of their treaties in the domestic legal hierarchy. They have also consistently expressed appreciation to States that have recognized human rights treaties as holding constitutional status, which is not always the case.

In its general comment No. 31 (2004), the Human Rights Committee explicitly noted the important status of international human rights treaties, which “flows directly from the principle contained in article 27 of the Vienna Convention on the Law of Treaties, according to which a State Party ‘may not invoke the provisions of its internal law as justification for its failure to perform a treaty’”. It noted that this principle “operates so as to prevent States parties from invoking provisions of the constitutional law or other aspects of domestic law to justify a failure to perform or give effect to obligations under the treaty”.

Reservations lodged by States that do not recognize the predominance of the Convention on the Rights of Persons with Disabilities if there is a conflict between it and their constitutional or national laws might present challenges in view of article 27 of the Vienna Convention. Consequently, even a State with a dualist system should at the very least not invoke national law as a reason not to respect the Convention, even if the Convention cannot be directly invoked in national courts without an additional act of parliament.