The Competence to Conclude Treaties in International Law and the Invalidity of Treaties within the Scope of Article 46 of the Vienna Convention on the Law of Treaties

The regulations governing the domestic procedures that states are to follow in their processes regarding the conclusion of a treaty represent one of the limited areas where international law intersects with domestic law. Nonetheless, the regulations in this area include various procedures. The power to conclude treaties, traditionally vested in the executive, has become a practice shared with the legislature in line with democratization processes. Constitutional courts or judicial bodies with similar powers may be able to be involved in these processes in some states. Other states even have treatyconcluding procedures that require a referendum. If a state becomes a party to an international treaty in violation these rules of domestic law, it may invoke the treaty's invalidity under Article 46 of the 1969 Vienna Convention on the Law of Treaties (VCLT). While this provision may seem to challenge both internationalism and constitutionalism, its practical application proves to be extremely difficult and rare. Both the complexity of states' rules on treaty -making and their diverse nature further complicates the matter to the extent that a general categorization becomes challenging. The study delves into the development, scope, and limitations of the relevant provision in VCLT and analyzes why this ground of invalidity, which was one of the most controversial issues in the preparatory work of the VCLT, is highly exceptional and unlikely to succeed if invoked. In addition, this study addresses the applicability of this provision to the rules on withdrawal from treaties that are currently under discussion in academia.